How do you finger a F note on the alto sax?

Start with your left thumb on the black circle on the back at the top... and your right thumb hooked into the hook at the back.

No fingers at all will produce the pitch of C#

Then, working downwards,

left hand

index finger being finger 1

Top/Left Hand

1 = B

1 and 2 = A

2 = C

1, 2 and 3 = G

adding Right/Bottom hand to 3 fingers down on the left hand

1 = F

1 and 2 = E

1,2 and 3 = D

Adding the speaker key (the one above the black circle operated with the side of the left thumb) will make all of these notes and Octave higher.

the operational range of the Saxophone is about 2 and a half octaves, covering from Lowest B to the highest F# keyed note. However, higher notes can be reached using harmonics/overtones and the altissimo register.