You can run it without any additional parameter.
If you want to use a specific speedtest server you can searh for its id:
Edit: I see you get an error:
Cannot retrieve speedtest configuration
ERROR: <urlopen error [Errno 99] Cannot assign requested address>
If it happens after retying it, you could specify a server id from https://www.speedtestserver.com/, but it seems the error happens before the retrieval of the server-list