for 220, you'll need to get a four wire line. When you did your 110V,
you probably used a 3 wire (red, black, copper). 4-wire is just like
that except you have an additional color, white.
To do it right, you'll need to find our the amperage requirement of the
hot-tub and, based on how far the box will be from the main breaker,
have to size the 4-wire accordingly.
For hookup, the 220V uses both busses on the breaker box, instead of
one buss for the 110V.
Go to your local HDepot, get a book on this, and they'll explain it
better than I can.