refugium build help

[Nascars]

I have a 40gal breeder tank and a 20gal long tank. I want to build a refugium with the 20gal long tank but not sure on how to start the build. I have a ati bubble master 160 skimmer that will be in there a kent marine float valve for my kalkwasser reactor also i have quiet one 2200 for my return. I have a over flow box for the 40gal tank. I'm not great on designing it. also will have cheato to. If some one could post some plans that would be great.