How do you get a winning point in 1v1 Riftbound? Can you just hold a battlefield and if it's still held at the start of your turn, and you have 7 points, then you have 8 points total and win? Do you just literally have to hold a battlefield to get a winning point?

Yes. If you're at 7 points and hold a battlefield at the start of your turn, you score to 8 and win immediately. No extra conditions needed. (Rule 466.1.b.1)

The only restriction on the final point is for conquering — you must conquer every battlefield that turn to win via conquest (Rule 466.1.b.2). If you conquer only one battlefield while sitting at 7, you draw a card instead of gaining the winning point.

But Hold has no such restriction. So yes — you literally just hold a battlefield at the start of your turn, reach 8, and win.