I applied to my first choice university directly

You will need to ask that Uni.
Direct applications by International applicants are uncommon and no-one here will know what that specific Uni requires.

Idk if I worded it right but on ucas it asks you to indicate what University is your first choice, insurance choice etc. I want to know how to skip picking a first choice on ucas and just pick an insurance since I applied to my first choice directly

Just put what you want as a "safety" choice as your firm choice on UCAS. They have no facility to consider any applications outside the UCAS system so if you ultimately meet the requirements for both you'll just tell whichever one you don't want to go to that you won't be attending.