I've been trying to figure out how to set up a timelapse and have seen that it might be possible to set up using my computer (Macbook Pro)
Yes! There are several applications available for Mac that can control a D90 over USB using the cable that came with your camera.
Here are two free options that support interval shooting. I don't use a Mac and can't test, so one caveat with Sofortbild: it hasn't been updated recently and may not work with newer cameras (should you upgrade at some point) or even newer OS X versions.
One limitation of these applications is that neither supports bulb ramping. This is a feature that changes the exposure over time, for example, to avoid a timelapse of a sunset becoming underexposed as the light fades. If you're interested in that, you'll probably need to look for a dedicated intervalometer or non-free software.
As xenoid mentioned in a comment, depending on your model of MacBook Pro, you may need to use an adapter to connect the USB cable to your laptop. If you don't have the original cable anymore, any USB A to B Mini (5 pin) cable will work (you will still need the adapter for your Mac).