This "jam session" is a D7 chord played over and over for you to get down all funky and play some blues.
"Stab" away with the left hand chord only
in time with the music.
Add D, F, G and Ab in the right hand.
Tip: Slide your 3rd finger off the Ab to G.
Play any notes from the blues scale.
Tip: Always play an G or A after the Ab.