The venue area determines the boundaries of your map. When you set a specific area for your venue, a satellite image projection is created to help you design your map at the correct scale.
You can control the position and opacity of this projection by clicking on the "File" icon on the bottom part of the left toolbar.
More on how to manage Overlays here.
To edit your Venue Area, click on the "Cog" icon next to your map's name at the top of the screen, then click on "Venue area".
From here, you can enter a new address for your venue.
You can also :
Once you are done, simply click "Ok" to validate.
A new satellite image projection will be created and a new Save milestone will be created.
More on saves here.