Before we head to the solution, let me explain what a regular proxy server is, in case you're not familiar with it.
A proxy server is a server that connects to services on your behalf and forwards all the results to you. After you've set up to route all your traffic through the proxy server, you—as a user—won't notice it's there. Everything will work as usual.
However, service owners only see that a certain machine (the proxy server) is connected to them. If another user uses the same proxy server and the same service as you do, the service owner can't tell the difference and will perceive you as one single user.