Rename group
If you are in the group details, to which you have access by clicking on the group name in the left hand menu panel.
You may now go to the group settings, which is located in the upper right of the screen and click on Rename.
A modal window will pop up, with the current group name in it, change it to whatever you desire and click on the Rename button.
info_outline Note that the group name has to be unique otherwise you won't be able to rename the group.