The correct position for the right arm is illustrated in Photo A below. Notice that the forearm rests on the upper edge of the guitar, just below the elbow. Be careful not to have the elbow hanging over the face of the guitar or your hand too far along the fretboard (Photo B).
The right hand is used to play the strings by picking or strumming them with a pick. A pick is a piece of plastic shaped like a triangle.
Hold the pick lightly between your thumb and first finger, as shown in the following photo.
For most rhythm guitar playing, th left hand thumb should be positioned behind the neck of the guitar with the fingers evenly arched over the fretboard.
All notes must be fretted with the tips of the fingers and positioned as close as practical to the fretwires.