According to my research, your keyboard has both a USB out for MIDI, and 1/4" stereo outputs.
If you want to record MIDI data from your keyboard, or use a synthesizer on your computer, you should be able to just plug the keyboard in with the USB jack.
If you want to capture audio data, you'll need to use the line out 1/4" jacks. What cable you use for this will depend on what inputs you have available on your computer and how much you care about audio quality.
If your PC has a standard 1/8" stereo minijack line in you want to use, you can use a simple stereo minijack to dual 1/4" cable. Alternatively, you can use the (possibly more common) stereo minijack to dual RCA cable with these RCA to TS 1/4" adapters. The latter is my preferred method for the extra options it gives you. Similar cables can be found at any Radio Shack.
If you do not have any audio inputs on your computer, you will need to use a USB interface of some sort. Here are a whole bunch, but avoid buying "guitar link" cables, since though they have 1/4" plugs on them, they will be prepared for a different kind of signal than the one coming from your keyboard. Many simple interfaces present RCA input jacks for which you would need a cable like this to connect to your keyboard.
Possibly the option you are looking for is the Alesis Dual-1/4"-to-USB LineLink cable. Looks like it'll get the job done with a minimum of hassle.
I was somewhat concerned with terminology for this, since the size of "phone jack" connectors is referred to in many different ways. This Wikipedia entry has some further information about nomenclature and usage for phone jacks of various kinds. In the following, I have included metric plug sizes. A plug with one black ring on it, separating two contacts is referred to as TS, for Tip/Sleeve. This is usually used for single channel audio. A plug with two black rings and thus three contacts is called TRS, for Tip/Ring/Sleeve, and is used for two-channel stereo audio. Your keyboard has the following connectors:
- USB: This is a standard USB type B port. USB cables have different connectors on each side to prevent plugging a host into a host or a peripheral into another peripheral. The flat rectangular port (Type A) is only found on a computer, or host. You can use a standard A-B USB cable to plug your keyboard into your computer. HOWEVER, keep in mind that this USB interface will only send MIDI signals. You will need to run a separate program on your computer to synthesize these signals into the sound of your choosing. If you are confused about this, you should probably go with a different option that will directly record the audio produced by your keyboard.
- SUSTAIN/ASSIGNABLE JACK: This is a 1/4" (6.3mm) TS, or "phone plug" used to send information from a foot pedal to your keyboard.
- PHONES: This is a 1/4" (6.3mm) TRS, or "stereo phone jack" OUTPUT. (The rightmost example of this image.) This would be typically used with a pair of headphones, but can also theoretically be used to output audio to something else, like your computer. It's not the best option though, since the signal will be amplified to drive a pair of headphones.
- AUDIO IN: This is a "stereo minijack," or TRS 1/8" (3.5mm) jack, for the plug seen second from the right in this image; also here. This is the kind of plug you would use with a portable MP3 player, and is also most commonly found on computer sound cards. This jack would be used to send audio TO the keyboard to pass through the speakers or headphones, for example, when you want to play along with a recording.
- DC 12V: Power connector.
- LINE OUT—R, L/MONO: Both of these jacks are for 1/4" (6.3mm) TS, or "phone plug," "instrument jack" connectors seen here. These will provide line level stereo (or mono, with only one the left plug in use) sound suitable for recording.
What to use:
If you're not capturing MIDI (as detailed above with a standard A-B USB cable), you need to use the "LINE OUT" jacks.
If your computer has a sound card, it probably has a stereo minijack (TRS 3.5mm or 1/8") line level input. (This would look the same as the "AUDIO IN" jack on your keyboard, and may be colored blue.) In this case you can use a stereo minijack (TRS 1/8" or 3.5mm) to dual 1/4" (6.3mm) TS cable to connect the "LINE OUT" jacks to your sound card.
If your computer does NOT have a sound card, or you want higher quality audio, then the Alesis LineLink is your simplest option. That product is essentially a USB sound card with dual 1/4" (6.3mm) TS plugs for input.