Run basic wizard. It will setup WAN interface on port 0, LAN ports 1-4 as an ordinary switch, DHCP/DNS server and firewall. The first part is very simple and router is ready to go. You can modify firewall/NAT later to suit your needs, but it not so simple like in home routers. It ads an abstraction layer by creating firewall rules first, then applying these rules. Not many people take it easy.