Usually you start GIMP either by clicking an icon (if your system is set up to provide you with one), or by typing gimp on a command line. If you have multiple versions of GIMP installed, you may need to type gimp-2.10 to get the newest version. You can, if you want, provide a list of image file names on the command line after the program name so that GIMP automatically opens those files after it starts. It is also possible, though, to open files from within GIMP once it is running.