Assuming you have a flat (single VLAN) network, you shouldn't need to do anything to the switch. From the factory, all ports are on the same default VLAN (1).
As far as internet goes, the switch needs to be connected to the router as there is no firewall in the 1234. If it is a 2nd generation 1234 and you have the latest firmware, you can do some basic routing with it, but it sounds like you just want to plug it into your existing router to get your LAN up and running.
If you're router is using multiple VLAN(s), then you should add matching VLAN(s) and set the port that links to the router into Trunk mode. I hope this helps.