Moin moin =)
your map is a she? =O
Anyway I bet you mean, how to increase the map size? In this case, make the following steps:
1) Go to the terrain editor [F3] > Scenario > Map size and camera bounds.
2) In the new window mark "Modify Map Bounds" (it's down left)
3) Now you can increase the size with the arrows you see in the same window.
Make sure that the value must be multiple of 32.
Greetings and Peace
Dr. Boom