1. make sure you link your Windows 10 to your Microsoft account: https://www.windowscentral.com/how-link-your-windows-10-product-key-microsoft-account. This will make reactivating your windows 10 key alot easier.
2. Create a windows 10 installtion USB thumb drive.
https://www.microsoft.com/en-us/software-download/windows10
3. Now, rebuild your PC with the new hardware. ONLY install the new SSD drive. Leave out your old drive for now. Due to the hardware changes, you need to do a new installation of windows.
4. Power up and make sure you can get into the bios screen. Set the boot order to an external usb. Power down.
5. Insert your usb stick, power up and install windows. Activate with your Microsoft account and do all the windows updates. Install drives for your mobo. Power down.
6. Power up into bios and set the boot order to the SSD drive. Power down and up again. Make sure the PC boots and windows is working, set your windows preferences, desktop, etc.
7. Now you can install your old hard drive and copy your personal files over to the SSD.
8. Here's info on how to remove the old windows installation from you're old/secondary hard drive:
http://www.tomshardware.com/forum/id-3474452/delete-windows-folder-hdd.html