When you log in as administrator, you have all available options. If I remember correctly, you first have to, in "Wireless Properties", open "New Virtual Ap" to get to the "Wireless WDS" screen.
From mentioned Pirelli manual:
"Virtual APs:
You can set up multiple wireless LANs on PRG AV4202N limited only to the number supported by your wireless card. Each wireless LAN is defined as an access point. The 'Virtual APs' section displays the Router's physical wireless access point, on top of which virtual connections may be created. To create a virtual connection, click the 'New Virtual AP' link. The new connection will also be added to the network connections list, and will be configurable like any other connection. You can change the connection's default name by clicking its Edit action icon and changing the SSID value in the 'Configure LAN Wireless 802.11n Access Point - Virtual AP' screen."
"Wireless WDS
It enables wireless bridging of access points within its range. Virtual access points are used to interact with router's WDS peers, granting LAN users access to remote wireless networks. When enabled, a WDS List box is shown."