HELP! Columbia University official rowing means letter?

Thank you so much! This really helps. So if the coach gives me a positive okay from admissions, would the coach be supporting my application on the common app and kinda helping me get into the school? And when I do the “staged” signing does that mean that I’m in?

Sorry this whole college-sports is so confusing. I feel that I’m a great and hard working student and you can see that in my grades and activities but I know my act is kinda low for them so I don’t want that test to not allow me to go to Columbia. So rowing makes up for my ACT