It depends on what firewall you're talking about. The windows firewall can be "configured" by double clicking your network icon (lower right corner in the systemtray) and choose Properties > Advanced > Settings... Configuring other firewalls that you may have installed on your system depend on the firewall-programs itself, can't help you there...
NIS = Norton Internet Security, another kind of "firewall"...
If all these things seems like Chinees to you and you own your own computer, then you proberly haven't installed them. If the computer is maintained by someone else, ask that person.
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