How do I configure proxy for my terminal with v2ray?

Taking a quick stab from the documentation:

It does not appear that v2ray will pick up from the environment the http_proxy env var, it needs to be configured via a JSON (or protobuf) file. There's an example client config file here.

You'd save that file somewhere, then run it in your terminal like this:

v2ray --config=/etc/v2ray/config.json (or wherever your config file lives).