As short as possible :

Web-Interface:
---------------
NAT Setting -> Virtual Server
Port Range: 9
Local IP: 192.168.1.10 (use your own ip-address)
Local Port: 9
Protocol: UDP
Description: WOL xy computer

Console:
--------
ipkg install net-tools

add
arp -s 192.168.1.10 01:02:03:04:05:06 (use your own ip- and mac-address)
to
/tmp/local/sbin/post-mount

flashfs save
flashfs commit
flashfs enable
reboot

Then wake up your PC using this web-page (or other):
http://stephan.mestrona.net/wol/

Good luck Eike