If you mean bridge via wireless I believe that functionality was taken out after the 1.03 firmware.
If you want to do a wired bridge (using the DIR-655 as a gigabit switch) can be pretty easily done. Just assign the DIR-655 a static IP internally that is outside of the DHCP range of your ADSL router (i.e.: your ADSL router assigns IPs in the range of 192.168.1.100 to 192.168.1.150, make the DIR-655 192.168.1.99) in Setup -> Router Settings. Then just turn off the DHCP server in Setup -> Network Settings.