Have you pre-registered your event yet? Once you pre-register, you will get access to the Organisers Only area, where there are heaps of resources to help you plan your event, as well as lots of other organisers to help you with information and ideas. .
Licensing requirements depend on the country, the type of venue, the screening media you are using (35mm film print vs. DVD) and whether you're charging a fee to attend the event.
Some countries have blanket agreements for educational venues such as libraries which allow them to screen films. You would need to check the laws and procedures for your country, but if you are in the US, as you are from an outside organisation and if the library does not have this license, they would need to have a Public Performance Site License from Movie Licensing USA (a division of Swank). Details on this are here:
http://www.movlic.com/library/faq.html. If they do not wish to obtain this license, you would need to contact to obtain a license. The cost for a license through Swank can vary depending on location, venue and other factors.