Invoke lrcfg and choose 1) Network configuration and then 1) Network Interfaces. In the interface file, comment all lines except those for the bridge.

(...)
#Step 4 (optional): configure a bridge
auto br0
iface br0 inet static
	address 192.168.1.254
	masklen 24
	broadcast 192.168.1.255
	bridge_ports all

The address is not mandatory for the system to work as a bridge but will be necessary if you want to log into the system and manage /configure /monitor the system.

Note: Please remember that all other auto configuration and address configurations for all other interfaces should be commented as they become slaves to the bridge and do not have an individual identity.