Any tips? How do I let them know the house is occupied and make them go elsewhere?
Assert your dominance. At sunrise, commence a territorial dance that shall last twelve hours. By sundown, the house is yours.
Well, you can keep knocking it down. We have one on the rectangular pendant light hanging in our front entryway. We had knocked the beginnings of the nest down, but two days later, there she was sitting on a fully completed nest. So it can be 12-14 days to hatch and then 2 more weeks to fledge.
Man, these birds are cute but oh so messy! We had problems with swallows making a nest on one of our porch light pendants. We knocked the half-completed nest down, and to prevent the builders from coming back, Mr. B temporarily put berry nets around the light. It worked.
http://www.doityourself.com/stry/eight-tips-for-keeping-birds-off-of-your-porch-lights#b
The only method I know is to keep taking it down…like daily…or more frequently. They finally get the message. It took me about a week.
Use the back door.
I would contact a wild life rehabber or someone in the ‘know’ about birds.
This is a great place to ask: http://www.pigeons.biz/forums/ Sorry, it’s not about robins (robins are not my specialty 
), but there are people that work with all sorts of birds, so they should be able to help.
At least you caught it early. We tend to use a side door to go in and out and birds built a nest in our front door wreath and laid eggs before we noticed it. We just left them alone at that point, but the crows got to the nest.
Also had birds build a nest and lay eggs in a potted plant on back porch. We had to water around them.
Maybe you can get some more ideas from here: http://www.pigeons.biz/forums/f5/help-pigeons-wont-leave-nest-on-balcony-68871.html
While we were away for a couple of weeks a little hummingbird built a nest in the planter next to the front door. Boy was she surprised when we came home. However, things are progressing nicely, we have two teenyweeny hummingbirds in the world. We put up some caution tape around the front door as well with a note “do not disturb our tiny friends”.
I kept catching the darn dog with his entire head stuck inside our chimnea…enough said. 
Keep taking it down, they do not lay just one nest of eggs more like 2 or 3 so you will have them for about 6 weeks. We have robins around our house too and they spend the day flying into our windows. We are waiting for them to get hurt doing so, it is really a problem. They have ruined our front porch with their droppings.
We had a big wreath on our door once that birds built a nest in. Didn’t seem to bother them when we went in and out although we usually used the garage door.
A robin has built a nest on top of the woodpile that’s right outside our home office. She’s not interfering with anything, so we’re enjoying watching her. She’s as big as a house right now!
They tend to build their nest at the same place each year. Or at least that is what I’ve been told. So give that some thought if you think you can tough it out.
We had a bird slam into our one window over 100 times a day constantly over and over. I don’t if it was brain damaged with all those slams. Well, anyways we put a stuffed animal on the ledge of the window. It stopped it.
However, next year the same thing again. It must have been the same bird again. There can’t be two stupid birds out there doing exactly the same thing to the window.
So last year we put up a hardtop sun shelter. The legs/post were hollow. A bird built it’s next on the top of the hollow part of the post. We let it go thinking it would eventually move on after the babies were born. One day, I think it was the daddy bird was watching over the babies and the bird fell down the leg/post of the shelter. There any room in there for him to fly out. He flapped for hours and hours. I felt awful. We couldnt do anything to help. He eventually died. Then, it decayed and smelled. Ugh.
However, in the past we had a bird building a nest in our wreath on the front door. Out came another stuffed animal. If I recall it worked.
That makes sense. They used to build a nest in a boxwood bush not far from the front door. The bush lost a limb over the winter and it became unsuitable for a nest. They make a mess in building a nest!
I’ll have to look if my D still has any stuffed animal.
wire mesh on top of the door, short length of garden hose (they think it’s a snake), aluminum foil (shiny reflective side startles them) or pie pan. balloons can work, too…they’ll lay 3 or 4 eggs once it’s done…and those take 2 weeks to hatch
they will build it in the same place every year if you let them, but robins only live about 5 years…
“I kept catching the darn dog with his entire head stuck inside our chimnea…enough said.”
We had wrens nest in our chiminea a few years ago. Now we cover if with a grill cover. We put up a bird house on the wall next to it. Have had birds nesting in it every spring since.
I would probably leave the nest in the front door be for now, but I am a sucker.
I would get a fake owl maybe it will scare the birds.