Pressing the camera icon at upper right should cause a Save As dialog to open. By default, this dialog saves screenshots to the desktop.
The screenshot file will save with the name "screenshot.png" unless there is already a file by that name, in which case it will save as "screenshot (1).png".
The screenshot file will save with the name "screenshot.png" unless there is already a file by that name, in which case it will save as "screenshot (1).png".