I thought I remembered seeing a way to submit a prospect through rolltide.com, but I couldn't find it just now.
I'd think the best way is to probably get him to come up for a camp during the summer. That's the way coaches find out about a lot of prospects. Not every kid is on PerfectGame, especially as a freshman (unless they go to a lot of PG events OR have someone create a PG prospect page for them, which most freshmen won't have).
If that's not really an option, you could always go here
https://rolltide.com/staff-directory and go to the baseball section and send an email about it. I don't know who the best option to send it to is though. Normally there'd be a "recruiting coordinator" but none of the assistants technically have that title (officially, at least), so I guess it would be fine to send it to any of them?
Sorry I can't provide a more definite answer. Hopefully someone else can chime in with better information.