Question regarding anchoring ropes in ice/rock climbing?

2 ways. Either one person goes up first and as he goes attaches things into the rock or ice (there are cracks in the rocks that will let them do that) as they go - for their safety as they climb, and when they get to the top they create a strong holding point for the others. If the climb is a long one they might need to do a couple of these part way up a rock face, then the other climbers climb and catch up then the leader goes off again. (generally if the leader gets to the end of his safety rope that's when that happens) Another way is for the person setting the top holding point to walk around the climb by another route and do it that way. Often with a rock face there is a gentler slope near it that gets to the same point and they can walk up that with the equipment, set up and then go back down to climb. This route can be used for the climbers to go down to have another climb if they want (instead of absailing)

My ice climbing is speleological. This tends to place reader at the top of ice or rock before descending. The best place to learn vertical ice speleology is Greenland in my opinion. I make do with ice screws on glaciers in USA.