The first D7 chord we'll play will use the same fingering as our G7 chord at the seventh fret. Now we'll play it at the second fret, which gives us the root note on the third string, and on the second fingering a root note on the first string.
When you play along with the jam tracks, play one inversion for four beats and switch to the other inversion for four beats. If these changes feel too fast, play one strum every four beats and then switch inversions. Remember to play through each jam track ten times.