The Focusrite should serve your needs well.
There are two main ways of using the interface with your keyboards.
1 Midi
By connecting the keyboard to the interface using a midi cable you transmit data from keyboard to computer. This data is information about what notes you play, when you play them and for how long. This data holds no actual audio information. When you've recorded it into your DAW, you can play with it: change notes, add and delete notes, fix up mistakes in playing and so on.
When you play midi back, you will hear nothing unless you give it something to play on. You can do this by loading a virtual instrument into your DAW. Or by sending the midi back to your keyboard (which means another midi lead (unless you swap ins and outs with just the one).
Think of midi like a paper piano roll, and something that will play it as being the pianola.
2 Audio
Your keyboard should have audio out as well. Most likely this will be a pair of 6.5mm line outputs. Using a pair of standard guitar leads, you can go from the outputs of the keyboard to the interface inputs, and from there, record the actual audio into the DAW. When you play this back, you will hear this through your interface (which is where you should connect monitor speakers to).
