Adding a gallery

SOrry I am new to WordPress….the developer that did the site for me took my money and has not been very helpful at all, I believe that they dont actually know how to use it properly. ANyway, I have a page which I wish to add a gallery to, but every time I try to, it does not add the gallery…using the “add Media” and “Add Image” etc….none of it works…the developer added two images to this page, but can I see “WHERE” they are?…Nooooooooo

I really am getting very fed up as either WordPress is no good or (as I suspect) my developer is a complete MUPEET and doesn’t actually know how to help me….

If anyone can help I would be most grateful