This following tutorial will tell you 2 ways to get console for CSS.
1. Easyest way to get console is to:
1.1 Go to Steams "My Games"
1.2 Press Counter-Strike:Source with RIGHT mouse button.
1.3 Then select "Properties"
1.4 Then press "Set Launch Options..." in "General" tab
1.5 Little Window should appear, write
in that box.
1.6 Press "OK" and start CSS.
Then the other way which is bit harder.
2. Hard way:
2.1 Go to your "SteamApps" folder (You can find it usually from: "C:/program files/(valve)/steam/")
2.2 Then navigate to: "SteamApps/(Your username)/counter-strike source/cstrike/cfg/"
2.3 Then open "Config" in notepad.
2.4 You should see lots of text in your notepad. Search for "bind "`" "toggleconsole".
(2.4.1 Press "control + f" to open searchbox, then write "toggleconsole" and press "search")
2.5 Now put any key you want to open console inside quotation marks, so it should look like this: NOTE: It can be any key you want, but if you put key which have been already binded, it will be replaced with this key.