The first two posts would apply if you had a laptop/PC. There is a button on the top row that says PrtScr. That is for taking a screen image. Then use right click and paste or Cntrol and V to paste the screen image you took into the online form. Or paste it into Word, wordpad or similar first.
I am on windows 7.
I found the prt sc key and pressed that to try to paste into paint but nothing happened that is why I said it did not work, I also tried serif page plus but again nothing happened