How quickly can you tone triceps?

Continue to restrict calories and do cardio to burn the fat.

On the strength training side you need to keep lifting heavy. Incorporate compound moves that work the arms good.

For example bench press (dumbbells in particular) work the triceps. You can adjust the focus by adjusting the angle of the lift.

Lat pulldowns and barbell/dumbbell rows hit the biceps good.

after the compound moves then it is worth your time to hit the isolation moves heavy if you have the energy.

Filling out the arms will give you a more tone tricep.

I don't know what equipment you have, but,

Lift heavy,
And do bench press. I like 5x5 myself. Floor press if you don't have a bench (laying on the floor...)
I like to finish my triceps off with push-downs from a bar on a cable. if that's not around I like tricep kickbacks.

I'll echo the barbell row too. It's a great one you should be doing anyway.

Push ups can help too.

Dips, skull crushers and tricep presses are good exercises too.