How do I enable a three column layout in XMonad?

I'm a Haskell and XMonad beginner. I'm trying to set up my tiling layout to allow three side by side columns (so that I can have three simultaneous tall and thin Vim instances for coding, per workspace). In the docs, I've found a three-column layout function , and even managed to import it and define a custom layout, but I'm not sure how to add it to my layoutHook, which already has some stuff defined from a tutorial I read, to keep my xmobar safe from window covering. The relevant lines of my xmonad.hs: import XMonad.Layout.ThreeColumns threeLayout = ThreeCol 1 (3/100) (1/2) ... main = do xmonad $ defaultConfig { manageHook = manageDocks manageHook defaultConfig , layoutHook = avoidStruts $ layoutHook defaultConfig ... How do I change the layoutHook line to keep the existing configs, while also adding my three-column tile layout?