You can add photos from the edit page. In your members control panel, home owners click the 'Edit your ad' link, house sitters click the 'Public profile' link.
If you are having problems uploading photos it's most likely because their file size is too large. They need to be less than 2 megabytes. You can reduce the size by using one of the many free image optimisation tools on the web, here is a link to one: http://www.imageoptimizer.net/Home.aspx