My hot tub is currently wired for 110. How do I convert it to 220? I need some specifics.

Additional amperage is needed to carry the load your looking for, check the hardware section, or the local electrical supplier for the correct amp circuit breaker.

Then new wiring must be installed,a 110 runs on a hot and common wires(ie 12/2 with ground)totaling 3 wires.

The new system will require new wire rated to handle the load(ie 10/3 with ground)totaling 4 wires.

Hooking the new circuit breaker to the new line requires a little finesse,patience,and all the power turned off(if you're a novice I wouldn't do this,a pro can do it without getting the bite from the power source,and in 1/4 the time)If your familiar with this type of work,a new Romex connector(probably a 3/4" to fit the larger wire)an open space in the box to run the wire in(punch outs located on the circuit box)and the stripping/connecting of:
A)hot wire(red)
B)hot wire(black)
C)common wire(white)
D)common wire copper

Red and black get connected to the hot connection on the new breaker.

Common white and copper connect just like the others in the box,on the pole section to ground.

The outlet(if you have a plug in) is hot wire on the left and right(in the housing)common and ground together in the bottom.

If this is direct wiring to a pump,etc,do what manufacturer suggests.

Others will say more if this doesn't help you enough.

KBC