Adobe Photoshop is the standard program for creating and editing images. If you don’t have Photoshop, use an online web app like Pixlr to create files. Here is how to open a new image file and adjust an image size in Pixlr:
Go to the Pixlr website
Choose "Create a new image" or "Open image from computer."
If you create a new image, enter the dimensions according to Mass.gov guidelines
Adjust the image size by selecting "Image" from the dropdown menu, then select "Canvas size." Enter the new dimensions, and select "OK" when done.
To save an image, select “File” from the dropdown menu, select “Save”, and enter the filename and format appropriate for the image. This will usually be a JPG. Select “My computer” or “Pixlr library” depending on where you want to save the file.