Here is a roadmap for administrators to quickly setup everything:
1 - You first need to create/edit your users.
Here is an article about setting up your users.
2 - How will your users make calls? IP phones / softphones or existing direct dial numbers?
You should have a list of all the users with the type of phone they will use. Then find out the data needed for each type of phone with this article about how to set them up.
5 - If you make a lot of calls then you will save a lot of time using Power Dialer.