Click the link below the entry box labelled Make a link ("blue clicky"). You'll get a new page with 2 boxes at the top. Put the address where your photos are in the top box (Link URL: eg http://www.google.com) and put anything you want as a label in the second box (Link text (optional*) eg Google search). Press the button marked Create Link. Copy the 2nd line it show you (eg <a href="http://www.google.com">Google search</a>) into the post - that will be your link. You can test that it's ok by clicking the link after Test this link: on the generation page.

Mick