Setting up your conference line in a few clicks. Start by clicking on "Main Number".

 
Conference Setup 

 

From here you can Add your a conference number by adding a spare or purchasing a new one.
Setup a Custom greeting if you want and let's move on over to the "Users" section.

Nav to "User Features -> Conference Bridge" amd Enable it.
Setup a conference room number and access it from the Main number displayed.

Conference Bridge