Second moment of inertia.

Hey guys!

I came across this question and its on second moment of inertia, which I totally don't know the first thing about. So I was wondering if you can explain it process from the start so I can do other problems too.

Here it goes:

A flywheel consists of a 10mm thick disc of diameter 90mm symmetrically inside a hoop with internal diamemter 90mm, external diameter 100mm and thickness 50mm. Both components of the flywheel are made from the same material and its total mass is 1078g. Determine from first principles the flywheel's second moment of inertia about a central axis perpendicular to the face of the disc.

As the question states 'from first principles' I also want to know what the easier method for finding the solution will be.

I hope you guys can help. As it seems like a tough question!