What is a button bar?

This may sound stupid but I'm trying to sync my music since apple took away all my music on my phones but my iMac seems to still have it for some reason. During one of the steps if I want to sync without plugging my phone in it says to go to "general settings in button bar." The picture they give is no help. I don't know how it varies over the versions so for context I have a 2012 iMac. Here's the link I'm referring to with the instructions that are confusing me. I'm sorry again I'm not a tech genius at all lol