Step 1: Get the user ID.
Assuming the user is logged in, which they would have to be to save data associated with their profile, you can grab their user id with the get_current_user_id function. That will be necessary, otherwise you're not going to be able to attach something to their profile.
Step 2: Create a front end page with a form.
I've done this before, using ACF, so I'm not 100% sure how your set up will function for this, but conceptually I had added custom fields to a profile with ACF. Then I made a front end form submission with ACF, and used its save post functions to push form field inputs to the posts, or profiles, as it were. This wasn't easy - I spent a lot of time doing it and I had to get really familiar with how WordPress user profiles worked.
Regardless, I don't think you're going to find an out of the box solution, I think you're looking at custom development. If that's not your wheelhouse, you'll want to hire a WordPress dev.