To create FTP application the must thing is you should have an IP address associated with that particular instance.
To add FTP click on Add-ons symbol and then click the install button.
Need to confirm the Installation in the Dialog box as shown below, once you the installation gets completed you will receive a auto-generated mail from Jelastic which will consist of the login credentials.
To login to Jelastic you can use the browsers or you can use the FTP application such as coreFTP, Filezila, etc. you can follow the given below link:
To Reset the password click on Reset password, to uninstall FTP click on Uninstall option.