This is the new chord for this level. The first finger is in the same position as in the A chord which is a nice way to first learn the chord. Do not to play the thickest 2 strings as shown by the ‘X’s in the chord box below- or it will sound bad!
The D Major Chord
Thumb position on the D chord
For now your thumb should still be behind the neck just creeping over the top (see photo above!) Later we will learn to use the thumb to silence (aka mute) the thickest E string for the D & the A chord. However, this will likely be too much of a struggle at this time. Its better to keep the thumb there it is until around level 3 or 4 of this course when the tiny muscles in your hand are more use to this new job you are asking of them!