First thing is a patent search. Much can be done with an internet search to research devices which may be similar. You may find a ton of products/devices/processes already in the same vein. Then you need to determine if you actually have a new product or an improvement that can be patented. How is yours different from everything else? It could be the way a mechanism is put together to make for smoother operation for example.
If you think you’ve got something totally new (or just a new part,process etc) you can start the patent process. A patent attorney can help here to give you a basic outline but I’m sure you can get a pretty good idea from internet sources.
You’ll need to write up the invention describing how it works, provide drawings, and explain what makes your particular gizmo different from others already on the market.
It’ll be sent (with a check of course) to the patent office who have experts in the field who will challenge you further by sending similar patents back to you requiring you to defend what makes your product (or improvement) original.
It can be a lengthy process because of sheer numbers of applicants.
In the meantime if you want to try marketing it you’ll need to have “patent pending” to protect (at least try) yourself. But from PP date I think it’s only a year to go for the patent.
In the meantime (if you pursue this) keep all your records of dates, drawings, prototypes, photos to prove you were first. If you think it’s a true winner (you won the lottery then) then I wouldn’t show anyone who wasn’t totally trustworthy including and especially schools or universities.