You need to use the form.
Name:
SteamID:
Reason:
Date & Time:
Admin:
Server:
Have you been banned before:
Screenshot URL (Use tinypic.com):
Other:
And Post your screenshot, you'l find it in the cstrike folder.
If your steamer, go to local disk C > Program Files > Steam > Steamapps > Common > Half-life > Cstrike > Search for the screenshot. (Regular Steam install).
If your non-steamer, go to the place where you have downloaded cs, you'l find Counter-strike> Cstrike.
If you cant find the folder, go to the game icon where you open the game, right click > Properties > Open file location.