can i switch my computer to a different apple ID

I just bought a MAC mini, The problem is I now have multiple apple id's.

I had an old one for my iTunes that I forgot about because my PC went down several years ago.

I purchased an iPhone and used my e-mail address for the apple ID. I have been able to

recover my old apple ID that was not used for a long time. expect now I have all my purchased music

on the old ID saved on the cloud (by assuming Apple set it up for me while the id was not being used).

When I tried to play the music from the cloud from my old ID, I got a message that stated

"This computer is already associated with an Apple ID"

"You can not download from a different apple Id for 90 days"

Also there was a transfer button available which I did not select.

What did that mean?

Does this mean in 90 days I will be able to get my old music on my new MiniMac.

Thanks for any help.

hdolores