Extract the zip archive using your favorite archiving tool
Step 3: Locate the folder for userdata
Locate your userdata folder, note that this is NOT the install location. This is the place xonotic saves your userdata.
Windows: C:\users\user\saved games\xonotic\data
Mac: ~/Library/Application Support/xonotic/data
This folder has a similar layout as the game folder. Game wise these data folders are treated similarly, however, it is best to save your work in the userdata folder so that you don’t accidentally mess up your Xonotic install, or so that your work doesn’t get lost in an update.
Step 4: Moving the mapping support pk3
The mapping support zip contains a file called xonotic-<timestamp>-maps-mapping.pk3. Move this file to the userdata folder (see step 3), NOTdata/data.
This folder should also contain your config.cfg.
Step 5: Get NetRadiant working
Windows: The mapping support zip contains a compiled version of NetRadiant in the mapping folder
Linux: Linux users need to compile NetRadiant themselves (see NetRadiant Repo) or can download a compiled version here
Mac: Current versions of MacOS/OSX don't seem to work because of gtkglext, compiled versions from here might work
Step 6: Setting up NetRadiant
When you first start up radiant it may ask where the engine path is. Simply, point it to the xonotic install location. Then NetRadaint should start,and the lower right pane should have lists of texture packs. If there are no texture packs, then refer back to step 4.