If your able to download then you can leave things the way they are. You don't have to change anything. Sometimes even with a firewall people can still upload from you. You just won't get as many as you would if you have them configured for limewire.
Does LW show that you have a firewall? Check the icon of the globe in the lower left in LW. Is there a brick wall in front of it? If there is, that means you have a firewall blocking LW and you'll need to configure it.
See these threads:
FIREWALL ISSUES Connection problems? Check here first!.
If you run into problems, post back with some info about your set up and we'll try to help.
OS(Win XP etc)
LW & Java version (help > about LW & you'll see)
Firewall you're using
Modem/router brand & model
ISP(Internet Service Provider)
Connection type (DSL etc)
Where you connect from (home, school etc)
Are you sharing a connection with other computers
Is this your first try with LW