NexGen gallery on non-wordpress page

Hi, i have some pages on my site that are not technically wordpress pages but i’ve used PHP to read from the wp-blog-header file, so wordpress functions can be run on them.

Im looking to use the nextgen gallery, but all i can find about how to show it is use [gallery=id] in your post. As i cant edit these pages in wordpress editor (i have to use html/php) what PHP would i have to use to get my gallery etc. to show up?