1. Open the Frozen Throne Editor of Warcraft and open the map to be modified.

2. Select the Map option in the toolbar on the left side of the editor.

3. In the map options, select "Map Information".

4. In the map information window, you can see the size and boundary information of the map. You can manually enter or use the slider to adjust the map size and boundaries.

5. After adjustment, click the "Apply" button to save the changes, and then save the map again.