And do you want a fresh Windows installation, or the original Asus OEM installation?
[/HR]EDIT: IF you come back and decide to follow up....here's the gist.
One-Drive System: Install the SSD as your OS drive, and re-task your existing HDD as the data drive. For installing the OS on the SSD, you have three options:
Perform a fresh Windows installation (using a downloaded installer ISO). This requires the most effort, because you need to install all drivers and programs manually, but it results in the "cleanest" installation, if that's your goal.
Use the recovery partition on your HDD to make a set of recovery DVDs, then use those DVDs to perform a factory restore on the SSD. This gives you the exact same installation your computer had when it first shipped from the factory.....with all the original drivers and Asus programs.
Create a system image of your current Windows setup, which is like a "snapshot" of it at the moment you create the image. Then install the SSD and restore that image onto the SSD. There are some tweaks required afterwards, to optimize an installation originally made on an HDD for use on the SSD.
With Windows on the SSD, you simply set it as your boot drive....and you'll be very happy with how much faster Windows boots this way!
Two-Drive System: The steps as above are essentially the same, but rather than adding the SSD, it will be replacing your existing boot drive and leaving your existing data drive in place.