Bring up your T-Mobile browser on your phone.
Click the menu key (key next to the pearl) and select Go To...
Enter
Google Maps
There you will get a screen that says
Google Maps
Download Google Maps
for the Blackberry 8100
Click the blue link by scrolling down with the pearl and press enter <-| key (Lower right) or by pressing on the pearl when highlighted.
Then you should get a screen that provides version information with two buttons on the bottom. Download and Cancel.
Scroll down to Download and press the pearl.
You need to have a data plan to receive the download and if you want follow me tracking, then an external GPS puck is necessary.