'Tr' means 'trill'. Play the note and the diatonic note above it alternately. As in DCDCDCDCD, quite fast, while the lower two notes are held only for the short quaver shown.  I'd be playing it with two hands (left hand is doing nothing else), so E and G l.h., trill,r.h., whichever fingers you are better with - the suggestion here is 5434, but there are other combinations.

The end of the trill is BC, up to D - that chord being basically G7, which can all be played easily with r.h.

EDIT: I've just realised where the question is coming from! Although the heads are on either side of the stem (F and D on left, G on right), all three are played at the same time - it's the only way the F and G can be written! Were all the dots on the same side, it'd look like an indecipherable blob.