Are you asking how to get the "Buy This Song at..." Link under the Video to the right??
If this is the case, most of the time, Youtube will "FORCE Monetize"ANY Video that includes Music that has a Copyright Claim (sometimes even take down the Video, or limit to certain Countries), but it all depends on the Copyright Owner's preferences.
This is GOOD for us musicians & producers because Youtube will give you a percentage of the Ad Click Revenues from ALL Videos uploaded that include your music. Even if it was someone else who uploaded it!!
HOW DO YOU GET YOUTUBE TO LINK TO YOUR MUSIC??
You need to Digitally Distribute it to iTunes, AmazonMP3, Google Play, eMusic, etc.
There are places that will distribute your music for you to ALL these places for you such as Reverbnation, & CDBaby - I think they charge a one-time fee or an annual fee of like $50 bucks.
So if you are an independent Artist seeking exposure, it may be a good idea to offer up a track or two for FREE to people to use in their Youtube Videos.
Once you get your stuff Distributed online, Youtube's Digital Signature Software will automatically detect when someone uploads a Video with your Music.