OK, I feel like this should be a question that I don't need to ask, but I couldn't find an explanation anywhere.
I am playing the full version of Dungeon Siege 3 (not the demo, which doesn't allow saving). I walked up to a save point beacon, and the game popped up a little "hint" explaining that this was a save point. But it didn't tell me what to do with it, nor did it appear that it had auto-saved when I touched it. I tried bringing up the game menu, but there was no Save Game option, only Load Game (and that only showed my last auto-save).
So how do I actually save at a save point?