From Motorola:

How do I use Latitude on my phone?

Latitude allows you to see where your friends and family are on Google Maps™. Your location is not shared unless you agree to it. You need to join Latitude, and then invite your friends to view your location or accept their invitations.
Before you begin on your phone, you need to have the latitude gadget added to your iGoogle homepage.
To do this, on your PC, go to this link: and select the option to "Add Latitude to iGoogle" in the lower right corner of the screen.
Note: The DROID uses the latest version of latitude so it is recommended to follow the steps above even if you already have latitude on iGoogle.
To Join Latitude:
When using Google Maps, press Menu > Join Latitude. Read the privacy policy and if you agree with it, tap Agree & share.
Add & remove friends:
  1. From the Applications menu, touch Maps
  2. Press Menu
  3. Tap Latitude
  4. Press Menu
  5. Tap Add friends.
  6. Tap Select from Contacts or Add via email address, then tap a contact > Add friends.
If your friends already use Latitude, they’ll receive an email request and a notification. If they have not yet joined Latitude, they’ll receive an email request that invites them to sign in to Latitude with their Google account.
To remove friends:
  1. Press Menu > Latitude to show your friend’s list, then tap a friend in your list.
  2. Tap Remove.
Share location:
When you receive a request to share location details you can choose to:
  • Accept and share back — see your friend’s location, and your friend can see yours.
  • Accept, but hide my location — see your friend's location, but they can't see yours.
  • Don't accept — location information is not shared between you and your friend.
Hide your location:
Press Menu > Latitude to show your friend’s list.
Tap your contact name, then press Menu > Privacy > Hide your location.
Turn off Latitude:
Press Menu > Latitude to show your friend’s list.
Tap Menu > Privacy > Turn off Latitude.
CLICK HERE to learn more about Latitude.