Screenshots created for iMac desktop upload to Dropbox and don't show up on my desktop

I have a new iMac.  I recently created a screenshot that I intended be viewed on my computer Desktop - something that was previously, always automatic. This time, I got a message from Dropbox which I thought was asking me to auto upload screenshots to Dropbox.  Assuming this was similar to allowing Dropbox to copy a file or photo, I allowed it, believing that the 
"original" item would remain on my computer.  I was wrong.  Every time I create a screen shot and attempt to keep it on my computer Desktop (regardless of the means by which I attempt to do this, e.g. drag and drop from finder) it "disappears" from my screen and is now in a Drop box file folder "screenshots".  I have searched various Dropbox settings and info sources, as well as those for Mac devices, and cannot find a place or means by which I can either stop this altogether or make sure that any screenshot I create can be maintained and viewed on my computer Desktop, as well as in Dropbox. Help please!!! 🙂