[Plugin: NextGEN Gallery] change template

Goodmorning, to chance the template I have to store it in the folder nggallery, inside my theme directory. Could anyone please help me where to find my theme directory.
My second question is if there also is a template or plugin with the photo gallery as on the following website: http://www.janmaartenvoskuil.nl/html/images/0000.html

Thanks for your help, regards, rubins

http://wordpress.org/extend/plugins/nextgen-gallery/