Accidentally created new Apple ID, how to merge?
So I've got an iPhone and iPad already, and last week got a new MacBook Air. In the setup process of this laptop I accidentally created a new Apple ID. I have no purchases on this new ID, so I really don't need it. I just want to stop using it and start using my old Apple ID on my new laptop. I got lots of purchases on my old ID. But how?! It seems impossible to change Apple ID on my MacBook Air.
I see some pages with descriptions on how to change from one user to another, like in case you're selling your MacBook to someone else, but then I'd lose the license for some of the software! I'm not switching users, it's still me!😢
MacBook Air, OS X Yosemite (10.10.4)