To make proxy and security settings available, please, activate
Advanced mode by enabling the corresponding button on the main toolbar. Then switch to "Proxy and Security" tab in the main window and you will be shown the following set of features:

Now tick
"Connect to remote host server via proxy" checkbox, choose proxy type you use (SOCKS4, SOCKS5, HTTPS) and input proxy server address and port.
If you want to enable proxy authorization (available when you use SOCKS5 or HTTPS proxies) just tick the correspondent checkbox and write in proxy server username and password.
Besides you can tick
"Redirect DNS requests to proxy server" checkbox if you want DNS name to IP address conversion to be done by proxy. If not, the local DNS is used.
Note, that these three options are available in "client" connection only.
You can enable traffic encryption in
"Security settings". It is recommended for security reason, all sent data will be encrypted, although it slows down the communication speed.
Besides you are able to enable password authorization while sharing a serial port for incoming connections. Note, that remote client should write in the same password in order to establish connection.