>How do I change the battery

Undo two screws on top of the handle, the hook bit covers a battery compartment

>how do I take the fork part off from the
handle.

The fork doubles as a thermometotr probe so is not removed.

You wash thermo fork keeping the handle out of the water (the thermo fork is 15 inch long)

>What size batteries does it take?

2 x AAA included!