What software are you running on your MacBook? What exactly are you trying to do? Are you trying to set up two-step verification or are you simply trying to authorize your computer in iTunes? Please add as much info about what it is you are trying to do and what you have done so far.
Apple > About This Mac
Per below article, they will show up in the Apple ID site as trusted if the device is signed into the correct Apple ID. But what allows them to show up is dependent on the version of iOS or OS X you are using:
iOS 9 or OS X El Capitan
Devices with iOS 9 or OS X El Capitan will appear in the device list if you're signed in to iCloud, iMessage, FaceTime, the App and iTunes Stores, or Game Center on the device. You can also see your paired Apple Watch.
iOS 8 or OS X Yosemite
Devices running iOS 8 or OS X Yosemite will appear in the device list only if you're signed in to iCloud with your Apple ID. You can also see your paired Apple Watch.
iOS 7 or OS X Mavericks and earlier
To see any devices running iOS 7 or OS X Mavericks or earlier, you need to be signed in to iCloud on the device and you need Find My iPhone turned on.
So make sure all of your devices are signed into the same Apple ID
Check your Apple ID device list to see where you're signed in - Apple Support