When first run, GIMP performs a series of steps to
    configure options and directories. The configuration process creates a
    subdirectory in your home directory called
    .gimp-2.8. All of the
    configuration information is stored in this directory. If you remove
    or rename the directory, GIMP will repeat the initial
    configuration process, creating a new
    .gimp-2.8
    directory. Use this capability to explore different configuration
    options without destroying your existing installation, or to recover if
    your configuration files are damaged.
  
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!