I am SO in over my head!!!

I am used to playing melody, but lately I'm interested in some songs that don't sound very good playing the melody~I think chords would be much better.  UGH I have NO IDEA what I'm doing!  Even with a chord chart~where do they go/start?  How do I strum?  I have a chord chart for the song I'm working on (guitar, I guess?) but am just lost.  Any advice?  Break it down Pre-K style, please....