0.6.2 doesn't have map selector support, so you'll need to download maps yourself. CS:S maps will work, CS:GO won't, not sure about TF2. You'll need to put the map files (.bsp) in your momentum/maps/ folder.
I'm not sure why you're using 0.6.2 though unless you're using SDR or something, 0.8.7 is the more recent public version.
