I would recomend making sure you know your notes on a staff at first and begin with Diatonic Chord Harmony and know/have the/a working understanding of what "makes" a chord.

Try to use 3 least references when learning this... i.e standard music notation, Tab , Chord "boxes", scale "boxes", and your git-fiddle.

There are some postings and threads plus I am sure there are lessons on the site to help get you started.