The sfp-cli may be slightly different than the CLI's that you are accustomed to using. Firstly, the sfp-cli is its own CLI, and not a plugin of the Salesforce CLI, which means that to start using it all you have to type into the terminal is
$ sfp. The other key difference is that the commands do not accept any flags or arguments. Sfp-cli is designed with an interactive prompt-based UI, which is as simple as following the instruction on the screen. Try it out for yourself by typing
$ sfp [COMMAND] in the terminal, substituting
[COMMAND] for one of the commands listed below.