1 - click on the green square with the smaller blue 'save' square over it.
2 - you can then choose a file from your computer or one from the internet
3 - choose the file format (I suggest forums)
4 - click 'host it'
5 - after that, choose whether you want a thumbnail, the image, or a link to the image. Copy what is written for whichever you choose and paste it here.
I wouldn't suggest using it on iOS