To enable passive ftp on an EC2 server, you need to configure the ports that your ftp server should use for inbound connections, then open a list of available ports for the ftp client data connections.
I'm not that familiar with linux, but the commands you posted are the steps to install the ftp server, configure the ec2 firewall rules (through the AWS API), then configure the ftp server to use the ports you allowed on the ec2 firewall.
So this step installs the ftp client (VSFTP)
> yum install vsftpd
These steps configure the ftp client
> vi /etc/vsftpd/vsftpd.conf
-- Add following lines at the end of file --
pasv_enable=YES
pasv_min_port=1024
pasv_max_port=1048
pasv_address=<Public IP of your instance>
> /etc/init.d/vsftpd restart
but the other two steps are easier done through the amazon console under EC2 Security groups. There you need to configure the security group that is assigned to your server to allow connections on ports 20,21, and 1024-1048