how do i set up my imac to purchase songs for the first time as it is asking me for passwords i did not set up
Are you talking about a password to log into the Mac, or a password to log into the iTunes store? I'll assume you mean the store.
You need to log in with your AppleID. If you created an AppleID, you created a password. If you haven't, then select the option to create an AppleID and password.
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