Hi Jeff,
Thanks for reaching out.
Please follow these simple steps to do that
Step 1) First of all, go to Appearance -> Customize -> Page Settings and select option Background Image in Choose Page Title Background Color or Background Image. Also make sure there is NO image selected in Select Background Image for Page
Step 2) Next, go to the Pages -> All Pages and open your page with the EDIT link option
Step 3) Now, on the right on the page, there is a column showing a Featured Image tab section. Upload image in that featured image section and save
Step 4) Repeat step 2 and step 3 for all the other pages
Let us know if you have any questions
Best Regards