A lot of beginners struggle with multi tasking, only last week a novice was trying desperately to incorporate tapping his foot on the floor whilst playing. Making it natural will take practice. Here’s a bit of inspiration:
Counting out loud, and singing:
Source: 6 Ways to Play the Guitar and Sing at the Same Time
Once you’ve mastered the basic open chords try the common ones used by famous guitarists.
Source: Open guitar chords
Strum chords and sing, here are some tips:
Source: BBC – Sing – Learn to Sing: Top Tips
An easy F major, beginners make sure the high string rings out clear.