When you want to advertise on a BBM Channel, you are required to craft a title for the post, add a photo, then a little description alongside link to the post.
Since you have limited space to write on, there is need to shorten the url. Use goo.gl to shorten urls. The goo.gl link will also monitor the number of clicks on that link, alongside several other data.
But on the Google analytics platform, traffic from BBM Channel will show up as unkown. You can decide to create a new source through the url before you shorten it by adding this:
utm_source=BBM&utm_medium=BBM&utm_campaign=BBM
Assuming the url was: myblog.com/
Make the new url myblog.com/?utm_source=BBM&utm_medium=BBM&utm_campaign=BBM
Using the Google Analytics tool, you will notice that a source with name BBM has appeared in the data.
You can use this method to track traffic across multiple channels too, not just on BBM. Remember, since doing this will make the url very long, always shorten with goo.gl