How to connect other hardware to Eleven Rack and make it work in Pro Tools 11

[TENM]

Hello

I am building a music studio in my home.

I have an iMac 27" custom made, from Apple.
The Eleven Rack from AVID w/Pro Tools 11
The Mbox3 from AVID
A small Behringer mixer unit
A pair of KRK Rokit5 studio monitors

And several vintage synth rack units from Roland and Korg, running through a standard midi keyboard/controller.

On top of that I also have Komplete 7 from Native Instruments, Sibelius 6 and Finale 2012 full version.

I know however, very little about connecting hardware the correct way and know almost nothing about how to set it up in Pro Tools 11

First of all I am wondering if the Eleven Rack and the Mbox3 can be connected to each other? If so, how do I do that and how do I set them up in Pro Tools 11?

Also how can I connect the Eleven Rack and the Mbox 3 to the Behringer mixer?
And how do I set that up in Pro Tools 11?

I am just learning by doing, like I assume, many others in my position have done before me. So I hope you bare with me, and can give me some helpful advice.
Right now I have a lot of equipment, but I am not sure if I have connected them the right way.

I have connected the Eleven Rack and the Mbox3 via s/pidif
I don´t know if that is correct.

So right now those two are connected that way with the studio monitors.
However the mixer is not connected to any of them. Any advice?