Edit the <AppManager Home>\conf\AMServer.properties> file using Wordpad or vi editor .
To change the Http port number, change the value in am.webserver.port=XXXX entry for example,
am.webserver.port=9090 to am.webserver.port=80
Similarly to change the Https Port you can change it in
am.ssl.port=8443 to am.ssl.port=443
Save the file and restart the Applications Manager for the change to take effect. Make sure to take backup of the original file before any modification.