Taking a screenshot.For Windows:
Look at your keyboard,beside F12 should be a button called "Prt Scrn" or something similar.Press that and you have it.
Mac:Hold Command+Shift+3 or to crop it, hold command+shift+4
Once you did that go to your paint software,and right click the canvas and paste.
The editor:
This is a FREE editor,so if you have a payed one you might want to use that.
Sign up to
https://www.photobucket.com/Once signed up you should have the option to upload your picture.
Upload it,it should have the option to put the title and tags,ignore it,you can do it later.
Now there should be "Edit" below the picture,click it and mwala. crop/edit the picture.
How to post it in forums.
Once you submitted it,it should bring you to the picture.There should be a share photo on the left side.copy the link on where it says forums.