Kurbstomper

Fairly simple and straight forward question, I would like to no how to download and install new maps for online matches. I see all these people with tons of maps that I dont have and I honestly couldn't figure it out myself so any help would be greatly appreciated.

Anything I try to start the game through the launcher I get a steam error that says "Application load error P:0000065343. This didnt start happening until I updated the launcher from 2.06 to 2.07

Ok now I dont know if this is more on my side then the launcher itself but I dont have the technical know how to figure it out. When ever I download the launcher and then try to run it I get this message "The windows installer could not be accessed. This can occur if the windows installer is not correctly installed" usually I would know that this is my problem, but it does not happen with other programs. So any help would be greatly appreciated and I thank who ever helps me in advance.