I had installed openwrt in virtualbox and installed 464xlat package and its dependencies.But i dont know to configure it how is it possible
I don't know much about it myself, but do you have a DNS64 and NAT64 enabled network that you are connected to?
Yes I have
Reading on internet it looks like you should be able to create a new network interface in LUCI and select 464xlat as the protocol. Can you do that?