I have had a lot of people asking how I take the pictures of my screen for the Month at a Time Class. It's a great way to document those little tidbits from Facebook and other social media sites.
On a MAC:
Hold down command - shitft - 3
This captures the entire screen and will save it to your desktop as a .png
I take my images into Photoshop and can edit it there.
On a PC:
Use the Print Screen button (might say Prt/Scn & SysRq)
I am not familiar with this so let me know if this is incorrect.
Hope this little bit of info can help you in documenting those social media moments in your life. :)