How do I print labels from my Macbook air?

Well, you will need an air print enabled printer as well as one that can print labels. So, check your printer here:

About AirPrint - Apple Support

And then check your manual for instructions regarding labels.

Previous comments about wireless printer configuration, unless you are using a USB to Gigabit Ethernet adaptor.

Although the OS X Contacts application has printing label capability, it assumes you are working from a specific address group of multiple (different) names. If you want a sheet of repetitive information, then you will need a dedicated label application from the OS X App Store. Two that come to mind in order of their App Store rating. Use the link to their website on their App Store page.

• Labels & Addresses (24.99USD) ****+ -- currently 50% off. Free trial from their website
• Labelist 8 (19.99USD) ** - Free trial from their website

Another option for label printing software is Avery Design & Print for Mac. It is free and works very well. http://www.avery.com/avery/en_us/Help-Center/General-Help/Avery-Design--Print.ht m