View all your segments by clicking Segments in the left sidebar.
Hover over a Static Segment and click Actions to add users to the segment, view users, email users, rename the segment or delete it.
Hover over a Live Segment and click Actions to refresh it, view users, email users, rename the segment or delete it.
To create a folder to organize groups of segments, click New Folder:
Once you've created a folder, you can move segments into it using the Actions dropdown.
See What are segments? for more details.