You're playing WoW, so you don't have one called Combat. You have one called FTL DPS Keys instead. You want to follow the WoW Quick Start Guide. The section of the WoW Quick Start Guide that corresponds to what he pasted is Quickly_add_many_hotkeys,_optionally_with_auto-assist.

I'm pretty sure what you're asking is covered in the Quick Start Guide, please check it out.