No Gallery

http://www.Bernese-Leslyn.com

I upgraded to release 3.5 and was shown the “Gallery” plug-in; it does not appear anywhere in the Dashboard.
Am maintaining/using the “Toolbox” theme.
I added two pages (“Roadie Images,” “Oscar Images”) for new pictures, based upon the “Maddie Images” page, but get the message “please add the custom field of ‘pcat’ and type in the the category slug for the items you would like this page to display.” The example shows “pcat/photography.” I added the category (finding no way to add a custom field) and suborninated the image pages to that category. Worked for a while, but now the message has re-appeared
If I attempt to add an image to a post, everything hangs and I must login again.
I’ve looked at the Codex pages for image insertion into posts, but the examples do not coincide with what I see on my screen.
Any assistance for this newbie is much appreciated!!!!!