If you want to make complex changes to a digital photograph you can either use a specific image manipulation software such as Gimp, XnView, Inkscape or Photoshop Elements. Or, for simple changes (brightness/contrast/cropping/colour adjustments) you can use features within an existing software such as the Microsoft Office. Please see the links below that offer instruction on a variety of image adjustments.
MICROSOFT OFFICE (WORD, OUTLOOK, POWERPOINT, EXCEL)
GIMP
https://www.gimp.org/docs/userfaq.html
XNVIEW
https://newsgroup.xnview.com/viewforum.php?f=17
INKSCAPE
https://inkscape.org/en/learn/faq/
PHOTOSHOP ELEMENTS