Shrine is Firelink Shrine I guess, the very first area
For backstabs, you have to exit out of lock on (not sure if it's
necessary, but I find it a
lot easier that way). Just keep locked-on, circle around the enemy until they try attacking and get vulnerable, and if you managed to dodge that and can get behing them quickly press RS to de-lock and RB to backstab.
You can stealth some enemies if they're not facing you and you go near them while walking slowly, but you do have to get fairly close and press RB before they turn around. Basically they turn around as soon as you get within the backstab range so you can quickly press RB as soon as they start moving and still land the backstab.
For parries, yeah, LB and if the enemy is stunned and you hear the sound effect, press RB to counterattck. The timing isn't super severe but you do have to do it right away and you must be real close. Not all attacks can be parried either, you should practice against sweeps rather than thrusts.