what do you mean with "but the login page showing office-extend"
you need to look at the AP and ME-WLC as two different devices wich have different IP-addresses
the local AP should register as a lightweight AP at the ME-WLC on the same physical device.
If you all ready have another ME-WLC active, the AP may register to this other ME-WLC in your network (and the local ME-WLC can function as stand-by controller)
also do you meen you login into
- the WLAN (the created SSID with a login screen)
- the controller (ME-WLC) after being connected to the WLAN?
- login into the AP (wich configuration is controlled by the ME-WLC