how to add images to a slider in generatepress

I added the CHPC slider plugin. Added it as a widget to a sidebar. But how do I now add images to the slider? Searched support first, but not finding what I need. True beginner...
Also, added grid-columns plug-in, but not showing as widget. Does this mean this has to be added as shortcode, in either content section or text editor widget for sidebar or footer? Tx for help, I tried forum searches first, but am having a hard time here. :)