The OS should be installed onto the SSD for you. Because of the way OSX is written I would suggest keeping your user data location to the default on the SSD. Then point things like iTunes to a "Media" folder on the 2TB HDD as well as other data intensive things.
This is because the user specific app data is kept in the users folder. So you will lose the benefit of the SSD if when launching apps you still have to wait for the HDD to spin up.
If you want to change the user data location it can be done in the advanced options (right click) on your account in System Pref.