Import the master image being used for the map. Resize the window using your mouse (bottom right) so you can see better.

1. From the Import menu, click on Make Tiles.

1. Click on Browse to select the source image that will be cut up into tiles. Here is the image I am using ruined_crypt.png
2. The destination will be set for you so I would just leave.

Here is mine setup ready to import.

1. This is set to where I have the file on my computer. Yours should be set to where ever you have saved ruined_crypt.png
2. Yours should be the same except for the first part which is where Steam has installed the game (D:\Program Files (x86)\Steam\steamapps\common\D20 Dungeons).
3. Click OK and wait for the process to finish.