how to configure backup node under aix hacmp

Run networker.cluster script on both nodes and configure backups for each physical node and virtual one as per documentation guidelines.

i'm not found this script on aix 5.3 with nw7.4.1sp1 client.

You are running rather old client - I do not have so old client to verify if script is there - it should be placed in /bin directory, but you may wish to check software compatibility guide and use some more modern NW7 version (which will be EOL anyway by the end of next month).