How to add an image gallery to WordPress

Back in the old days it was difficult to add an image gallery to a WordPress website. Furthermore it was even more complicated to make the gallery look good or change the photos or drawings in the gallery once the gallery was created.
Fortunately it is now really simple to add galleries with varying great looking layouts to WordPress pages and posts. The video below shows just how to add one or more galleries to your WordPress pages or posts. The galleries work well with JPG, JPEG, GIF and PNG files.