Not able to upload images to sliding door pages

I havr tried for months to upload images to each sliding page. The original blog images from the 5 Sliding Door theme are still in use, at least 3 of them, but I cannot add more images. I have just realized that I had some categories instead of pages, so I was able to add pages, and edit them, and I have even added an image, but the image will not display in the home page of my blog. What am I doing wrong?