Before creating a crag, it's best to check if the crag you want to make topos for already exists on 27 Crags in order to avoid duplicates. Try by searching both the name (top left) and the location on the world map (browse map).
You can create a new crag or take maintainership of an existing one from your team page by clicking "+" and "add a crag or boulder area to maintain". Existing crags will show up in a drop-down list.
You can also create a new crag from your profile. If you do so, you still have to take maintainership. You can do this from the crag page's "edit" button, or from the team page like above.