Continue along the side
Once the corners have been taken, the next place where it is easy to make territory is the edge of the goban (Go board). The edge is also the place, next after the corner, where it is easiest to make eyes.
It is often said that along the side, groups can build a base. If a group has a base on the side it is said that it is, for now, strong and settled (opposite of unsettled). Later on in the game maybe the group will need defending, but for the time being it can be used to extend from, attack from etc.