Actually your photographs are already large enough.
To make them clickable you are supposed to to edit the post with a markup trick. It is very simple to implement! When you add a photo to post, it looks something like this:


All you need to get clickable image is to change the format as following:
[](image address)

You add square brackets around original format and then copy/paste image address in circle brackets after the enclosing square bracket.

Try editing layout of one of your posts that way and see what happens :)