RA2 maps on Steam

[rouxthless]

hi fellow commanders i started playing red alert back in the late 90's when it first came out.
 

i just bought the collection on steam, but i can't figure out where to install maps for red alert 2. does anyone know which directory they should go in? i tried putting them in the root directory for the game. i also tried creating /maps/custom and putting them there. neither of which worked. i have the game installed here:
 

D:\SteamLibrary\steamapps\common\Command & Conquer Red Alert II