Drag Background Objects onto the Map Workspace and then edit colours and add Background Text.
The Blank Map Template in File> New includes pre-formatted background objects so you can always start with that and edit the objects.
To avoid the background shapes moving around as you edit your map always Lock the Background with Design >Lock Background.
You must always Unlock the Background in Design Tab to be able to edit the Background objects.
See how to add and edit background objects. (Also see Adding images to background objects)