Enter the server's hostname and the port your FTP server is listening on (if you haven't changed this you can leave this field blank and Deploy will use the default port 21).
Then enter your username and password, and enable the option if the connection is Implicit. Next enable the option if necessary to Ignore TLS/SSL certificate errors (you will need to do this if are connecting using a self signed certificate).
DeployHQ will connect to your server using TLS v1.0 by default, but if you need to connect using a specific version you can select it via the TLS version dropdown. Enable passive mode (PASV) if your server supports it, then if your FTP server doesn't report hidden files such as .gitignore by default, you can enable the option to Force the server to report hidden files.