Downloading JPG files into Portfolio's secondary category

First of all, I am new in website creation, but I am long time user of Adobe Photoshop and Lightroom. I am trying to create my website with Portfolio. I made several galleries and decided to create 2 subgalleries in one major. I created covers for these subgalleries and I when I clicked on one of the subgallery's cover the program gave the window with the clickable thumbnail to make a photo grid with possibility to download my images. I downloaded several of them with a success, but the problem began when I tried to preview the page. I didn't see the photos and when I went back to editing I didn't see downloaded pictures anymore. I can preview my major page "Home" with the photo and clickable link to other pages. I didn't publish the website yet. I don't know what I can do to remedy this problem. Please help if you know how.

Thank you,

Andrey Skripchenko