This walkthrough covers Ableton Live's Preferences > Audio tab, the control center for connecting an audio interface. Pick Core Audio on Mac or ASIO on Windows as your driver type, then choose your input and output devices from the two device menus.
Sample rate gets its own selector here too, set separately from the driver choice. The real decision point is buffer size: Live defaults to 512 samples, but dropping it lower cuts latency so your playing and monitoring feel more responsive, at the cost of higher CPU load.
There's no universal right answer, it's a tradeoff between feel and stability that depends on your machine and what you're doing, tracking live input versus mixing a finished session.