What computer do you have?
I have "windows 7"
Windows 7 has a" snipper tool "Like This...
If you have this...you can "snip" or make your own caps ...from an online Video.
Other computers have the same capabilities...cut I can only speak for windows 7,
If you have this tool ...pin it to your taskbar.
Then when you click on it...you will see a small window on your screen.
Clich on "New"..and the Video freezes...and the screen becomes semi opaque ...
Select you Cap...and Save.
Joe..different computers will vary,
I found the snipper tool for mine...by "googling" .."how do I take a screen capture ?"
When you find a way..be patient ,
A lot of it is Trial and Error...till you get what you want,
Hope that helps ,