You need 5 cells, 1/3AAA in size. The best ones we have found are made by GP, they do both 120mAh and 160 mAh. They then need soldering together like any pack of cells, and connecting to a spare channel or bat socket in you reciever. You only need the positive and negative (no signal needed). You should put a switch of some kind (usually an old esc one) in line with the positive wire.

Depending on esc you usually then leave the esc switched off and only switch the reciever pack on, this will then power both esc and servo. Some esc's need to be switched on, but if that is the case you usually disconnect the positive wire from the esc's reciever plug and then switch both switches.

I only switch the pack on and leave teh esc off. I know this method works for LRP quantum comp and GM SX12.