Once you have clicked the "Add a base" button on the Headless CMS home page, you will see the panel below. 

For this new base, you can specify

• A name
  (required) This name will appear everywhere the base is used, including in Composer, so choose a name that is clear and easily distinguished from other bases. 
• A description
  (optional) Aids understanding for why this base was created and perhaps provides insight for how to use it.
• An image
  (optional)Make the base easily recognizable on your Headless CMS home page. 

You can edit these properties at any time, even if you have already used this base in an experience in Composer.