Your scanner should have a program that works with that specific scanner. If you do not have the software on hand, go to the products company website (epson, brother, HP, etc) and locate the software on their website. Once you install the software, you should be able to scan.
As for the types of documents you can scan into (the type of file that the scanned image is saved as) you have, but not limited to, JPEG, JPEG2k, PDF, IMG, Bitmap, etc.
Your image editing program, be it PhotoShop, MS Paint, etc.. under the "File" menu, the will be a selection to "Select Source" and this is where you will select your scanner (considering you have installed it's needed software to operate).
Next, under the same "File" menu, there should be a selection to "Acquire" or "Import" and here you will go to launch your scanner program and perform the scan into the imaging program you have open. After the image is scanned into the program, make sure you save the scanned image as a file to use later.