It was easy Katex. Can't understand why you can't do it.
Is your prt scr button in a box?? If so, when you use the prt scr button you have to press the fn button at the same time. The fn button is bottom left next to the ctrl key.
It is easy in Paint. After doing fn / prt scr (*at the same time) , Just open Paint and do ctrl / v * and it will appear. Go to Save As and save as whatever title the pic is to be called. Then upload to your hearts content!!
