Hi Tina, I apologize for the slow reply! :lol2:
Keep in mind I am forced to work on a limited budget, but the principle would be the same I suppose even for the nicest of systems.
Essentially it is very simple.
The refugium (in my case) is sitting on its own separate stand (wifes chest-of-drawers! lol) which is higher than the display tank it is connected to. The design could be nearly identical even if the add-on tank sat directly above the display, all installed into a single cabinet... which is my goal eventually!
The bare essentials needed are: Supply pump (somehow attached to feed water from the display to the refugium) and a return (somehow attached from the refugium back to the display).
For my return (your design and results may vary) I drilled a hole in the upper left corner of the new tank to accept a 1" ID bulkhead fitting. From there I installed a 90* street elbow and attached a 24" long piece of 1-3/8" ID clear tubing to serve as the return.
I used a Maxi-Jet 1200 slightly submerged into the upper right hand corner of my display, and the appropriate length of 1/2" ID tubing to connect it to the new 'fuge.
I fabricated a spray bar just shorter than the length of the tank and mounted it securely using various pipe threaded fittings found in the "sprinkler section" of your local hardware store (and a zip-tie :bigeyes

This is a shot showing the spray bar during "power-on mode" as it is just filling the refugium to its overflow level, once full the spray bar is submerged so no more bubbles...
And finally, the "Pucker Moment", which is when you get everything all hooked up and fire it off for the very first time... being sure once you think it is finally ready, to cycle the power off/on a few times to verify you have everything properly adjusted as far as water levels are concerned... hoping for no leaks (from your new system and its plumbing) or unexpected flooding (from powering off and having the water volume in the plumbing of the newly plumbed upstream display exceed the capacity of your main display!) e:fun5:
Mine's working great after a couple minor mods here and there, and some tweaking and adjusting... been running around 2 weeks now and already I have introduced a thriving sand bed, 7 different macro algaes, loads of Amphipods, Copepods, mini brittle stars, 5 species of snails, a few mini hermits, and several other various forms of life that are just starting to EXPLODE! :thumbsup:
