Can we use our octopus card to ride the airport express train going to yau ma tei .

Yes, of course you can use that card on local MTR.
You can only take the airport express line to Tsing Yi Station and then change to Tung Chung Line to Lai King Station. After that you need to change to Tsuen Wan Line to reach Yau Ma Tei Station.
Currently, if you use the octopus card to take the airport express, you can take the next journey from Tsing Yi to Yau Ma Tei using the MTR system for free. It means you need only to pay 60HKD from airport to Yau Ma Tei if you use airport express and the mtr system.