You have to "load the clicker" first!
You do this by clicking and treating and repeating many times, and do this randomly.
At some point you can wait till they are busy looking away at something else and not at you, and click. If they look at you for a treat, you know the clicker has been loaded successfully!
If you go on Youtube. Look up "Kikopup" if you want lots of funs things to train your dog- she is amazing and clicker training and using positive reinforcement.
For treats you will want to use different types and "values."
When you are in your house with no distractions, which could be doors opening, other animals, other people, etc. If you have NO other distraction you can probably use their own kibble as a treat.
A high value treat could be boiled chicken, freeze dried treats, natural balance rolls cut up into small pieces, etc. High value treats are usually when your working on something really hard.. Like for my dog when being in the same room as a stranger. Or when your working outside on the sidewalk with distractions.. cars, people, cats, strollers, etc.
You just need to find how easily distracted your dog is. What treats are the absolute favorites, etc. Lots of resources on clicker training on here and on youtube.