First, choose and install a proxy for the client you wish to use. Chrome has many options. Many of them are available as extensions, such as the NordVPN extension that @Madhu mentioned. You may also try searching for others, e.g. via the chrome webstore.
Once you've installed the extension:
mitmweb
(which you did). For anyone else who's reading this, the output will look something like the following, assuming you're using the default configuration:Web server listening at http://127.0.0.1:8081/
Proxy server listening at http://*:8080
http://127.0.0.1:8081
(which you also did).http://127.0.0.1:8080
.At this point you should see the traffic captured in the proxy web server. If you don't, review your configuration. Check the protocol, any filtering and switching rules, and the port (if specified).
In my experience, you can use the same Chrome browser who's traffic you want to capture as the client for the proxy web server. It may depend on which extension you choose.