What version of Premiere Elements and what computer operating system?
What are you importing into this project - photos (what pixel dimensions and how many) and video (frame size and frames rate and other format details)?
Are your imports portrait or landscape oriented when first imported and viewed in the Edit area monitor?
If you go to Edit Menu/Preferences/General do you find the preference Default Scale to Frame Size enabled (with check mark) or disabled (without a check mark)?
What are you manually or the project automatically setting as the project preset (project settings) to match the properties of the source media?
The simple answer is to click on the Edit area monitor to bring up the image's bounding box and then use one of the bounding box's handles to scale the image to fit the space (as best possible) in the monitor established by the project settings.
But the simple answer is probably not the right answer. We need to look at source media properties and project settings to determine what you have and what needs to be done.
Please review and consider. If any questions, please do not hesitate to ask.
Thank you very much. I will look at these points