The standard spoiler is part of the hinge for the boot and is easy to fit. You need a 10mm spanner or ratchet and somebody to hold the boot. When buying a spoiler make sure it comes with all the brackets.
Undo the 2 10mm bolts holding the boot lid on
Prod out the two nuts that are on the outside of the boot lid if they've not fallen off already
Fit the spoiler and re-attach the two 10mm nuts. This is the most important bit, make SURE you don't over tighten the nuts, if you do you will smash the boot lid. Its probably a good idea to use a spanner as its easier to get carried away with a ratchet.
If you've not got the seals put a bit of silicon round the hole to make it water tight.