Review and edit mode
In Review mode, you can explore the map, but you can't edit it.
If you only have View access to a map, you'll only be able to access the map in review mode.
But if you have Edit or Admin access to a map, you can switch between review mode and 'edit mode'.
Any new map you make will be in edit mode by default, so you can changes to your map.
To switch between edit mode and view mode, click the toggle in the top right: