Open up DevTools using /open_devtools and click on either "Garages" or "Impounds" tab, then navigate to "Create New" button.
Filling up the form
Here you need to name your garage, we suggest to start with the "Label" context, since name is automatically generated.
Additionally you can already apply permissions to the garage such as player or job.
Preparing coordinates
In the next stage you need to point to the proper coordinates, such as main target location, blips position and spots coordinates.
All keybinds are described in the left bottom corner.
Finishing
If you're satisfied with the location, hold ENTER key for 2 seconds and garage/impound will be automatically created and saved in either shared/config_garages.lua or shared/config_impounds.lua file.
