Select "Use proxy before connecting to the Tor network" on the Proxy Configuration page ->
Choose the proxy type ->
Fill out other necessary information
1. Proxy Type
The proxy type is the protocol which is used to communicate with the proxy server. Since there are only three options, they can all be tried until one works.
2. Proxy IP/hostname
It is necessary to know the proxy IP for attempted connections. If the user is trying to connect to a local proxy, then 127.0.0.1 should be specified since it is the localhost.
3. Proxy Port number
It is necessary to know the port number for attempted connections. It should be a positive integer from 1 to 65535. If searching for the listening port number of a well-known censorship circumvention tool, it can be found online.
4. Username and Password
If the username and password are unknown, they should be left blank to see if the connection will succeed. In most cases they are not needed.