This is a sample configuration to configure a Cisco autonomous AP into universal workgroup bridge mode.
This mode connects to a pre-existing WiFi network and bridges the connection to the Ethernet port. The MAC address referenced on the station-role line should be whichever device is attached to Gi0 (such as a desktop computer or router).

Note: In this role the AP won’t be reachable via the WiFi network – unless it is the only MAC on the link.

dot11 ssid WiFi
   authentication open 
   authentication key-management wpa version 2
   wpa-psk ascii 0 Pre-Shared-Key

interface Dot11Radio0
 no ip address
 encryption  mode ciphers aes-ccm 
 ssid WiFi
 antenna gain 0
 station-role workgroup-bridge universal 0011.0022.0033
 bridge-group 1

interface GigabitEthernet0
 no ip address
 duplex auto
 speed auto
 bridge-group 1

interface BVI1
 ip address 10.0.0.1 255.255.255.0

ip default-gateway 10.0.0.254

bridge 1 protocol ieee
bridge 1 route ip