Auto-translated
Winner, extract the archive into any folder, but preferably on the same drive as the installed game. Specify the path to the sourcemedia folder. The editor.ini file should contain something like this:
sets ~sourcemediafolder "C:\_games\kbaddon\sourcemedia"
In the editor itself, open the textures tab; there will be a list of textures divided into groups. Select the desired groups by double-clicking; the font of the groups should change to bold. After that, you will see the list of textures itself.
To increase the size of the location, you need to click "resize landscape" on the Landscape tab, and then expand it by the desired number of squares in the desired directions. The default map size is 4x4. The starting location in Legend is 12x12 squares. It is advisable to increase the size of the location when no changes have yet been made to it. Otherwise, the editor may freeze (or may not). You also need to consider one detail: the size of the location does not change instantly, but over some time, perhaps within 1-2 minutes; the developers did not provide any progress bars for this. You just need to wait until the editor displays the already changed value of the ratios. If you click on something during this time, it may also cause the editor to freeze or crash.