I have a discovery rather than a range so not sure exactly but there are usually two fuse boxes on cars, one under the bonnet marked fuses and one in the cabin somewhere, often behind a panel under the steering wheel... in my discovery the fuses are pretty well labelled so you shoudl be able to identify which one is for the satnav/stereo from the labels assuming the range is the same.. there may well be two, one in each fuse box as in a lot of cars the permanent live is fused under the bonnet and the ignition switched supply is fused in the cabin.. not looked at mine to see if landrover do that..
when you find the fuse there will be a fuse removal tool nearby,
like this:
Land Rover Brand New Fuse Removal Tool on eBay, also, Land Rover, Car Parts, Cars, Parts Vehicles (end time 20-Oct-08 22:55:06 BST)
but for heavens sake don't go buying one if you can't find it, the fuses can usually be pulled out by hand although they can be fiddly..
pull out the fuse you want to check (ignition off) and look at it..
blown ones look like this:
not blown ones haven't got the gap in the metal bit in the middle..
if it's blown replace it with a new one of the same rating (same colour = same rating) they are pennies to buy in any motor factors and your local petrol station will probably have some as well..
could have saved myself all this typing - watch this...
How To Replace A Blown Fuse (Cars: Routine Maintenance For Cars)