These are the instructions on how you add a Camera Static Overlay to SFM.
Basically, I will go through steps that will enable to do this. If you done it right, you will be able to see a sort of static blurry figure in your program, that means it is working.
1.) Open up SFM

2.) Open up any type of sessions like new or recent

3.) Open up a map by right clicking (ONLY when it's empty and needs a map)

4.) Go to the shots at the bottom with a blue colour

5.) Right click the yellow clip inside the blue clip

6.) Right click on the yellow clip

7.) See 'Edit Clip' (There must be a lot of option in there then it would be right)

8.) Don't click on it, just touch the option and wait for another dialog or popup to appear

9.) The arrow will lead to a smaller set of options

10.) Go to the bottom and see 'Set Clip Overlay' (I don't know what the alpha one does but do test it because it may be the same thing)

11.) There will be a selection of overlay options avaliable. Go to 'fnafgmstsa\camstatic.vmt'

12.) Search for that and an option will appear for the Camera Static Overlay

13.) Click on that and BOOM! The MAGIC has appeared to your viewport screen

14.) Have fun with the scenes :)

These instructions is what I tested on SFM and what I have learnt recently.
Hope this helped all of you