It’s easy! To Create a Collection, you can go to the bottom of the left hand navigation and select Create > Collection

From there, you will be prompted to name the Collection and add a tagline (optional).
You can also create a Collection by going to Network Settings > Spaces and Collections > View Collections and select the “+” icon.

Next, you will want to add Spaces to your Collection.
To manage your Collections, check out the article “How Do I Manage My Collections?”