8 weeks is a great time to start clicker training. although I do have a few issues with the length of this training session!
You can reward with toys but to start with it is better and clearer for the dog to learn the clicker with treats.
Simple guide to clicker training:-
The dog offers a behaviour eg sit you click immediately and then treat - simples 
To start with just click and throw a treat. I generally never ever fed my dogs from bowls, all meals are training session. So first day just click the clicker and throw a bit of the dogs meal.
Once the dog realises the clicker means good stuff they will try to make the click happen. You are now rolling!
I think luring is great to start with. So if teaching a sit lure into a sit by holding the treat above the dog as the dog sits click, gradually stop luring and the dog will then offer the sit, do not ask for it, do not say the sit, just wait. When the dog has worked out its behaviour makes the click you can then start freeshaping.
Re barking when someone knocks on the door. I would work on offering an alternative behavior rather than try to stop the barking. So get someone to knock on the door, have the dog on a lead and run to his bed and give the best treat ever. DO this time and time and the dog will run to his bed when the door is knocked rather than bark.