When first run, GIMP performs a series of steps to
    configure options and directories. The configuration process creates a
    a user-writable configuration directory named
    GIMP, with a per-version subdirectory,
    i.e. GIMP/2.10. All of the
    configuration information is stored in this directory. If you remove
    or rename the directory, GIMP repeats the initial
    configuration process, creating a new
    GIMP/2.10
    directory. Use this capability to explore different configuration
    options without deleting your existing installation, or to recover if
    your configuration files are damaged.
  
The configuration folder will be stored in:
          $XDG_CONFIG_HOME (defaulting to $HOME/.config)
          on UNIX platforms, except macOS;
        
          %APPDATA% on Windows;
        
          NSApplicationSupportDirectory (usually ~/Library/Application Support) on macOS.
        
Just a couple of suggestions before you start, though: First, GIMP provides tips you can read at any time using the menu command → . The tips provide information that is considered useful, but not easy to learn by experimenting; so they are worth reading. Please read the tips when you have the time. Second, if at some point you are trying to do something, and GIMP seems to have suddenly stopped functioning, the section Getting Unstuck may help you out. Happy Gimping!