What is needed from the client side:
Instance URL
API key
Basic authentication username (only if basic authentication is active on the instance)
Basic authentication password (only if basic authentication is active on the instance)
To enable the API-style authentication, you have to check Enable REST API in Administration -> Settings -> API.
You can find your API key on your account page (/my/account ) when logged in, on the right-hand pane of the default layout.