Under normal classic conditions, the b/w photographic paper is put into a chemical solution (developer) to make the image visible.
Not so when you are experimenting with Solargraphy.
The exposed paper is scanned in a dark environment (special darkroom light can be obtained) and developed in Photoshop.
It is advisable to prepare, and do a test with an other piece of paper, preferably one that is stiffer and is the same size as your b/w paper.
My experience is that it is best to tape an L shaped template on top of the glass of your scanner so it is affixed and stable.
You will next run a test with the template and a piece of paper (the same size of the b/w paper that you will be using), letting the scanner determine where the final place of the b/w paper is going be on your screen.
This way you can safely run a high resolution scan with just one scanning, without risking the image being influenced by the extreme light source of the scanner.
Hereby a picture of how I solve this problem.
It tells more than a thousand words…