i know you have to find the base note, but from there, how do determine what other frets to play?

It falls under the category of trial and error.

Find the base note, the remaining notes are going to be higher or lower - so find them. Is it the one directly under the note you are playing? is it a couple of frets higher?

TBH you should just look at Tab'd chords, much easier way of learning lol

i have the biggest problem with this, sometimes if i know the chords in the song, and im listenening to the song to get the strumming pattern, if its electric guitar thats in the song, i have trouble even figuring out where the chord changes are knowing in advance what chords are played

then again i never play on electric so it i guess thats part of it