Clicking on the thumbnail once should take you to a bit larger version in the album. Clicking on the image in the album should load the full resolution image.
Alternatively, you can place a linked medium sized image right in the article, which would probably be even better, like this:
Do you know what resolution the files are you uploaded? They appear to be 400 high and 600 wide now. If the ones you uploaded were larger than that, I think I know what the issue with it is and we can get around that.
Let me know that much, we'll take it one step at a time.