The battery + and - will have to be checked to the wiring/connection point to the actual radio using a test lamp or multimeter.
If you suspect a fuse then you are going to have to obtain a wiring diagram (from a Haynes workshop manual?) or take a close look at all the fuses to either visibly check each one or test using a test lamp or multi meter.
There are sometimes symbols on the fuse box casing which might help.
RegWorts, July 2008