Also see the Online Help files https://docs.pteavstudio.com/
You can easily resize images by going into Objects & Animation (O&A) and when an Object is selected you will see the Grab Handles around it.
Simply drag these with your mouse to resize as needed.
If you have several images all the same size then you can use the Quick Slide Style.
Do the first Manually, then 'Create Quick Style', Select all the other images & 'Apply Quick Style' and they will be resized accordingly.
PTE is a great program, very easy to get started but extremely powerful allowing you to do anything you can imagine.
Jill