Here is the FTP client that we suggest to everyone. It works perfectly with our servers.
Please download the software by going to the following link:
After installing the software, open it, go to File >> New >> New FTP Site. Then give the Label as your Site name, host address as your domain or our server shared IP which is 18.104.22.168 with your ftp username and password. You will be able to connect multiple site using this software and should be able to save FTP login details for multiple site.
Let us know if you need any further assistance from us.