Clear password

enable
set password enable clear
set password exec clear

Erase current configuration

enable
set nvram erase
write
reboot

Set bridging mode

enable  
set bridging rfc1483 enable
write
reboot

Set PPP mode

enable

set password enable <enable-password>
set password exec <exec-password>

set ppp wan0-0 ipcp 0.0.0.0
set ppp wan0-0 dns 0.0.0.0
set ppp wan0-0 login <ppp-user-id>
set ppp wan0-0 password <ppp-password>
set ppp restart enabled

set int vip0 ip <gateway/router-ip-address>
set int vip0 mask 255.255.255.248

set nat enable

Turn off Web server

set web disabled
set web port 6666
set web remote <remote-ip>

Turn on TFTP server

set tftp enabled
set tftp remote <remote-ip>

Enable DHCP server (optional)

set dhcp server enable

Save new configuration

write
reboot