How do you replace the brake light on an Opel Corsa 1999?

Depending on the model, B C or D there are some differences. The C model has lights on the rear pillars - access is by removing the two screws - see weblink for details. If it is a model with conventional lights ie below the window, access is via a panel inside the boot area. Remove the panel, remove the connector and replace bulb with the correct type. The bulb has small lugs like an household bulb, it will remove and replace with a twist action. Some bulbs are combined stop tail lights, so check at the accessory shop.