It should connect to to the hot.
Some dishwashers have an option for heating the water, but most don't
And if you really want hot water, you should run some out of the faucet first, before turning the washer on.
Otherwise it will fill with cold water until the hot line unloads. Since a dishwasher uses so little water, unless you purge the line, it's going to be cold or luke warm at best.