How can I add/move icloud contacts to a group?

On iCloud.com, open Contacts. Then, click on the ribbon with the people icon until the groups appear. Now, hit the plus icon at the bottom, and name the new group. Click back on "All Contacts". Now, simply drag each contact that you want to move into the group. If you want to select more than one at a time, just hold down the Command key (control key on Windows) and click on each one, then drag them all into the group.