We use Informers for that.
To create the Informer for the Most Popular Threads go to:
CP » Informers » Create Informer (located on the top right)
Give informer the proper name ex. "Most Popular Threads"
For Section: select Forum
For Sorting Mode: select Most popular threads
Create and Paste the code in the forum where you want it to appear. You can edit the design of the informer by clicking on [Informer template]
