First find a gif on google (easiest way is to put "gif" after your search word for an example if you want gifs of minions search for "minion gif"
Then you press pictures and press at a picture,if it starts to move its a gif if not press the right key to come to the next picture
When you find a gif you like right click on it and press copy pictures webbadress or something (i have google in swedish so not sure what it says)
Then you press the img button and between the [img.]http://And[/img] put the pic web adress you just copied
the first [img] should not have a dot but then the thing would be invisible so i put it there
Hope i did it good enough for you to understand