I think of when I was basically knowing to sing and play guitar thinking how on earth people could sing and play guitar same time. Heck, it was difficult learning guitar, let alone learning to sing and remember all those words and a melody overly!
It wasn't until about five years so far that I ever seriously commenced learning to sing and play guitar gravely and I was really pushed into it too. I set up a guitar/keyboard duo at first as some fun and as the keyboard player won't sing then I finished up to sing and play guitar same time, and I tell you I now love it!
Without blowing my own bark I can more or less now sing and play guitar thus right here are 4 simple things that I found have guided me as I go along:
1) Start with quite simple, strum-along songs. A real easy one would be something like "Summer Of 69 by Bryan Adams" or "Father & Son by Cat Stevens", just decide for yourself!
2) Learn how to play the chords first.
3) Learn the lyrics completely. This for me is the key. If you are having to read or endeavoring to remember lyrics you will really struggle. I'm don't comfortable until I have the lyrics nailed down.
4) Don't get worried greatly regarding being word or melody perfect. I occasionally find that rephrasing the speed of the lyrics fits much better with the guitar rhythm so make the song your own!
The great thing is that you will also realize that learning curve is very quick. Once you can perform just some songs then many more will adopt easily.