What program are you working with, Photoshop Elements, Premiere Elements, or something else, what version and on what computer operating system?
You have posted in the Premiere Elements Forum whose focus is video editing. Could you be wanting to know how to scale a photo once it is imported into Premiere Elements?
If you have Photoshop Elements and you want to change the resolution of just one photo, then see Photoshop Elements Full Editor, Image Menu/Resize/Image Resize and its dialog. If batch resizing, then check out Full Editor/File Menu/Process Multiple Files. Please check out the Adobe document on Help\Resizing
If you have Photoshop Elements, please direct your threads to the Photoshop Elements Forum
If this is a Premiere Elements workflow question, then please supply more details.