Q: how do I change primary iCloud account on our macbook air?

Hi kristen177,

If your husband has his own Apple ID, then all you will need to do is sign out of your account and sign into his for iCloud data (contacts, calendars, etc.)

You can choose to use one Apple ID for your iTunes Store purchases, or keep them separate as well.  See the articles below for more information.

Using your Apple ID for Apple services

http://support.apple.com/kb/HT4895

http://support.apple.com/kb/HT5622

Cheers,

- Judy