I think this needs explaining abit better.
1: You will need a way of installing windows so either a USB stick or DVD. USB is faster and ideal if you dont have an optical drive. (Depending on OS and Motherboard you may want to set up your windows
USB for UEFI mode)
2: Unplug the HDD from the motherboard and plug in the SSD.
3: Depending on your motherboard and OS you will want to set your bios to AHCI or UEFI as mentioned in step one.
4: Set bios to boot from either your DVD or USB depending how you are installing windows.
5: On install choose to install on your SSD.
6: When system reboots automatically pull the USB/DVD and set bios to boot from your SSD.
7: Once windows is all done and dusted plug in your HDD and still booting from the SSD move any files you want to keep over onto the SSD.
8: Then formant the HDD and rename it say "Storage". In there stick a few folders for say your games or movies etc. This will act just like say a external HDD or USB stick. Will have no programs on it or anything just whatever files you stick on it.
9: When you install any game you direct the install to go into your games folder on your HDD. Also Origin and Steam can be set up to install games in that folder also in the settings.