A to F#7
How to transition from an A chord to an F#7 chord.
The A → F#7 transition is the same V → III7 move in the key of D.
Chord shapes
Play the A chord in a A shape, and transition to a partial barre F#7 chord for a simple transition. Rotate your first finger to move from pressing on the D string to barring the 4 high strings on the second fret, then move your second finger up one fret.
AFull
F#7Partial barre
Anchor fingers: finger 1 on D string (fret 2)