From wherever you are on the platform, navigate to your Community's current name in the upper left corner and click Settings.
Under General, locate your current Community Name and change it to the new name you choose. Click "Save Canges" at the bottom.
To change the Community URL, click the "Want to change your community URL?" link and follow the prompts.
NOTE: URLs are unique and based on availability. If your name is already takes we suggest you add the word, Hub, Space, Spot, Community to the name.