If it's a deep scratch, we'd advise getting it done professionally. You can usually do a fairly good job with the right materials when it comes to light scratches, but for a deep scratch, it's often more hassle than it's worth if you have to buy all the materials and learn as you go. It's up to you if you want to have a go yourself, so obviously it's worth getting a quote to see what the alternative cost would be to employ a bodyshop. To do it yourself, you'll need to do plenty of research and use sandpaper or a rubbing compound on the area to smooth it out before you build up the colour and clear coats.