I'm trying to setup domain mapping for my multisite.

Hi I'm trying to setup domain mapping for my multisite. I've Installed the domain mapping plugin found here.
https://premium.wpmudev.org/project/domain-mapping/

The problem I am having is i can't get the domain Mapping Option to appear on my sub site under the tools menu.

Any ideas on what I might have missed in setting this up?

thanks,
- Kris