I know I am a bit old school, but I do it this way,
I will use "print screen" then paste into MS PAINT. ( I have not tried the snipping tool, but I am sure it is better)
Once in MS Paint I crop the image I want. I will then resize to pixels. The larger setting no more than 750. I then save as a JPG
In the forum below the edit window there is a button "Upload Attachment".
Imagine the Possibilities of a Creative mind