As to start out, i'll make a tutorial on how to get the console in CSS.
About: The console is the shell of CSS making you able to see what it does, and input some commands, it's like CMD for windows.
Follow the steps, and you'll be allright :)
Step 1: Open up your steam.
Step 2: Right click on "Counter-Strike: Source", and click on "Properties"
Step 3: Click on the 2nd bottom button with the text "Set Launch Options"
Step 4: Type in: "-console", and press ok twice.
If you got any questions, feel free to comment below.