First of all, welcome to the musical madhouse.
I can't sing, so I'm handicapped from the start, but the only thing that helps is practice. Practice the chords until you can play the song in your sleep - then try to build in some of the words, it's easier if you can find a hook in the song (maybe a particular chord change) that starts a certain phrase. It may help to play the song on a CD player or on your PC, whilst you play along and listen to where the words caome in relation to the chords.
I've been torturing myself with "Willie and the hand jive" - I reckon that if I can groan in sync with that
rhythm, I can get along with any tune!
I'm about 80% there, but certain phrases still cause me to lose the plot