You'll need to know the List ID that you want to link to. You can find this within CB > List Management under the ID column to the far right. Next you'll need to use it in the below example usage.
Code:
<iframe src="http://YOUR_DOMAIN/index.php?option=com_comprofiler&view=userslist&listid=LIST_ID_HERE&tmpl=component"></iframe>
See the below for additional iframe usage information as it has many attributes you can use to customize its display.
developer.mozilla.org/en-US/docs/Web/HTML/Element/iframe
For best display of a userlist in an iframe I recommend configuring the below by editing your userlist within CB > List Management.
Parameters > Search
Searchable fields: No
Parameters > Display
Show List Selector: No
Parameters > Paging
Show pagination: No
Parameters > Linking
Allow Link to Profile: No
This should make the userlist basically display purposes only and very little or no interaction as any links in the iframe will navigate the iframe.