This is a brief tutorial covering the Offline maps functionality within Google Maps.
Open Google Maps and select the Preferences button as indicated below:
This will bring up the menu of available options for Maps.
Select the "Offline Maps" option as indicated below:
Select your own Map
Using the commands as listed below, either drag or zoom to adjust the area required for download:
Confirm if the area is correct, and select Download as indicated below:
This will initiate the file download to your device
You can also view the status of the download.
Until it has completed successfully