Hi Doris ............... the D/F# doesn't mean 2 chords ........ it's called a "slash" chord.
It means a regular D major chord, but with F# in the Bass instead of the more usual D.
Instead of the usual D F# A D (building upwards from the D in the bass)
it would be F# then D F# A D (again building upwards)
If you're playing on your own .......... you would voice a regular D Maj chord plus you would play F# on the bottom string second fret.
If you're playing with a bass player ......... you just play D Maj as normal and let the bassman play F#
Hope that's ok ........... 'cos I'm just a Sax player :o)))