Welcome to the wondeful world of video editing Simon! You'll have many years of hair tearing ahead of you.
Your DCR-HC90E is a miniDV camera. So far, so good, but what does this mean to you? Well, it means getting the footage from your camera to your PC is simplicity itself: all you need is a firewire card and a firewire cable; chances are you have at least a firewire port on your PC.
Look for a connections like this:
If you don't have one of these slots, get a fire wire card
Next you need a firewire cable (your camcorder will have a 4 pin connector and your PC likely will have a six pin connector - so you'll need a 4-pin to 6-pin cable). The link provided above comes with a free cable. Wohoo!
So now that's the Camera connected to the PC. Soon you'll be experiencing lossless video on your PC ready to edit. To get the video on your PC (and to edit) you'll need some editing software. Again, the above card comes with a free version of Ulead's Video Studio. Not a bad option, but I suggest you download the trial version of Premiere Elements and get yourself a good guide from Amazon.
Premiere Elements will allow you to capture, edit, author and burn a DVD all in one application.