How to create subdomains
First you have to login to your control panel. When you are in, you will see this option:
Click there and you will see a box that says create a subdomain.You just have to write there the subdomain name.I wrote example
Then you have to click on create. After few seconds you will get a message saying it was created.Then you have to go to the home again.And the click in this option for create the FTP account:

When you click you will see this, you have to fill the login as the name of the subdomain (most recommended), and then fill the password and how much quota you will give to the subdomain:

Click on create and it is done!