How to open the acces gateway?

You can always try "anonymity proxies" like TheCloak, but if the firewall is really well configured, you will have a really hard time trying to fool it.

Moreover, note that by using a secured network like the one you seem to be on, you might have agreed to some code of conduct. Such agreement often have clauses that trying to go over security is a breach of contract and doing so could put you in trouble. Note that if you don't have any idea on how to fool security, you might not be "good enough" not to get caught.