Are you talking about the Harley Siren?
If so it's fairly easy and comes with instructions. One thing, the instructions tell you to remove the rear wheel. This is not necessary. You only need to remove the plastic front part of the rear fender (2 screws), to access the mounting area.
Installing the system is no problem.
Security system is plug and play replacement for turn signal module. Siren plugs into that. All mounts in front of rear wheel. Like previous post said - no need to remove rear wheel as instructions say, you can work around it by removing bags and plastic fender part. Took me about an hour. A little easier if you've got the manual, which makes it easier to find the turn signal stuff to begin with.