This post will be very general, because it would definitely depend on what kind of printer/scanner you have and how it was setup.

Commonly, if the printer has a scanner, and the full software for it is installed on your computer, you would typically have an icon on the desktop called Scan, or HPScan etc... doubleclick and off you go.

If you have no such icon, you could try this:

Go to Start, and then Devices and Printers

Find the Printer/scanner you are looking to scan from

Right click on the printer/scanner and their may be an option there to do a scan.

If not, some work may need to be done to enable scanning.