Controlling access to dashboards in workspaces

A real beginner question here .

I even done this before , but forgotten how. I've been running round in circles searching the website.

I used the "Manage menu" part of BridgeIT to add a dashboard to the self service menu , but i dont want everyone who sees the self service menu to see that item on it .

How do i restrict that dashboard to users in a certain group or role?

thanks,

-mark