Welcome to Tom's Hardware, @zelanthis89!
Installing the SSD is like installing any other hard drive really. It uses the same connections and can be physically setup the same way. However, since you plan to have your OS onto it, I'd recommend a fresh install. In this case, you will need to unplug the HDD from the motherboard (via SATA cable) until the Windows installation is completed. This is how you will avoid the OS confusion, which basically scatters the system files across all the SATA devices connected to the motherboard. You should be able to use the same OS and activation code, you are simply changing the booting drive, so the same OS version should work flawlessly. Before beginning, though, make sure the SATA mode for the SSD is set to AHCI and it's in the boot priority before the HDD.
However, you should definitely backup your files from the HDD before beginning the storage configuration update. This is the surest way to avoid any potential data loss. After you have Windows up and running from the SSD, connect the hard drive to the motherboard and use
Disk Management in Windows to re-format it. This procedure will erase all the files on it, including the old OS. Once the reformatting is completed, connect the backup drive and copy back all your needed data onto the HDD. It's also advisable to
change the default download/install path to the HDD, so that you don't fill the SSD with random writes.
Here's a very detailed step-by-step tutorial you can use about
Windows Install & Optimization for SSDs & HDDs.
Let me know if you have more questions! Best of luck!
SuperSoph_WD