It is generally a good idea to consider the final destination for your project, e.g. display on the Web. How you intend the video to be viewed will impact decisions you make in the early stages of the project.
Many modern web-based media players, such as YouTube, use an aspect ratio of 16:9, resulting in video at the following resolutions (in pixels):
Width x Height
640 x 360
720 x 405
854 x 480
960 x 540
1024 x 576
1280 x 720
1366 x 768
1600 x 900
1920 x 1080 - Full HD
When obtaining media for your digital story, it is generally best to get the highest resolution possible. Resizing all images prior to production will eliminate the black bars from appearing to the sides or top of the final display:
Load the original image, Load > File:
Resize the image, Image > Image size...:
Uncheck the "Constrain Proportions" option and set the pixel dimensions to Width: 1920 and Height: 1080:
Save the new image in the desired format.