Multi-Site Configuration Questions

I want to set-up multi site config .. mainly at the moment in order to get a Super admin log-in for buddy press, etc.

is there an easy way to do this that does not require a lot of complexity?

I have at least two sites that I want to metwork together .. but is it possible to also set-up multi-site without adding another site?.. I know this may sound strange, but I am trying to get the functionality of Buddy press working, but can only do that if I log-in as superadmin , which I can only do if I have Multi-site enabled.. Is that correct?

I am kind of confused - as maybe you can tell.