Youtube has a number of videos that can introduce you to GIS.
If you want to take a course, try searching on GIS MOOC (Massive Open Online Course); try
www.mooc-list.com/.../gis. Coursera offers a course ($$), but you get a yearlong license for ArcGIS (non-commercial).
Similar to ArcGIS, but free is QGIS, www.qgis.org. Tutorial at
www.qgistutorials.com/.../, and Youtube.
If you want to make simple maps, for desktop and mobile, try Google My Maps. Whatever you can do in Google Maps, e.g., find points of interest or get directions, you can add to a map, have it wherever you log in, and share it. Here's one I made for a trip -
drive.google.com/open
Also, OpenStreetMap, www.openstreetmap.org, allows you to contribute to an open project. You can even map your hometown or community.
Wanna volunteer? Humanitarian OpenStreetMap at www.hotosm.org; Missing Maps at www.missingmaps.org; The International Network of Crisis Mappers (Crisis Mappers Net) at crisismappers.org; USGS National Map Corps at
nationalmap.gov/TheNationalMapCorps