Address: For 99% of all cases, Automatic is the correct setting here. Shareaza will automatically determine your external IP. This even works if you are connected through a router using port forwarding. If you have multiple network cards, or you have multiple Addresses bound to one Network Adapter, you can specify the address that Shareaza uses. This is the address on which Shareaza listens for incoming connections.
Port: Here you can set the port Shareaza uses. The default is 6346, but there is no performance benefit is using this port rather than some other. You may wish to change your port to some other number because some Internet Providers are limiting bandwidth on this standard Gnutella port. Also, some BitTorrent trackers do not accept people advertizing this port (likely because the trackers' ISPs filter on this port). You can use any number higher than 1024 (you can use lower ports as well, but lower ports are more likely to interfere with other services running on your computer). If you have a direct Internet connection without a firewall that needs to be configured for a specific port, then you can safely check the Random checkbox. This means that at every startup, Shareaza will choose a random port on which it will listen for inbound connections.
Speed: Set the downstream bandwidth of your connection here. Make sure that the unit is correct. KB/s means kilobytes per second while Kb/s means kilobits per second. If you have a 56k modem select 7 KB/s or 56 Kb/s here.
Address: The address Shareaza uses to establish outbound connections can be set here. But again for 99% of all cases Automatic is the correct setting here.
Speed: Set the upstream (upload) bandwidth of your connection here. Make sure that the units are correct. KB/s means kilobytes per second while Kb/s means kilobits per second. If you have a 56k modem select 4 KB/s or 32 Kb/s here (Downstream bandwidth is higher than upstream on a 56k modem). User who don't know their speeds may wish to try an online speed test (dslreports' speed test links).
I can accept incoming connections: If this setting is on auto Shareaza will initially assume that you are using a firewalled connection unless Shareaza can determine that you can accept incoming connections -- it is therefore safe to leave this setting on auto even if you are not firewalled, or if you have a configured firewall. Users that are in a college network, or behind a NAT/Router/Gateway should always have this box on no or auto. In rare cases, where Shareaza insists you are firewalled, even though you know you are not, this may be set to yes. Shareaza is usually right though. See the Firewall FAQ page for more information on configuring firewalls or routers.
Ignore private/local IP addresses: If you want to run Shareaza inside a LAN, you should uncheck this. Do NOT uncheck this if you have a LAN connection to the Internet and only want to use Shareaza over the Internet. If this is checked Shareaza ignores private IPs (like 192.168.x.x, 10.x.x.x, etc) for connection attempts, and always requests a push from hosts reporting such IPs. However, if Shareaza is run on a LAN with private IPs and wants to connect to another Shareaza client in the LAN, then this setting should be unchecked.
Enable UPNP devices setup: Enabling this setting allows Shareaza to try to automatically configure upnp enabled firewalls or routers to allow Shareaza's traffic. If the router or firewall doesn't have UPNP capability, or it's been disabled, then this setting will have no effect.
Connection: This is the time in seconds Shareaza waits until a connection attempt fails. In general, it is not a good idea to change this value.
Handshake: This is the time in seconds Shareaza waits until a handshake attempt fails. You should normally not change this value.