Satellite Pro C-50A (SSD Problems)

My wife has a Toshiba Satellite Pro C50-A running on Win 10 Pro and I decided that (being a good husband) I would add a WD M2 SSD to make things a little quicker.

I don't want to remove the HDD as there is too many photos etc so I purchased an DVD Drive Caddy, installed the SSD and it all went together quite well.

At first it wasn't being recognised in the BIOS and it wasn't showing up in Windows either but I found out how to initialise the SSD it's now showing up in Windows but still not listed in the BIOS.

I've also downloaded Win 10 Pro on to a thumb drive with the Win Installation Tool and went through the steps in doing a clean install but when I got to the setup window asking where the OS should be installed, I selected the SSD but received the following message:

Windows cannot be installed to this disk. This computer's hardware may not support booting to this disk. Ensure the disk's controller is enabled in the computer's BIOS menu.

I then asked everybody's best buddy (Mr Google) what could be done and although I found some solutions, I can't find the appropriate option in BIOS to change the settings that have been suggested in various forums etc as I can't find the same terminology in the Satellite's BIOS.

It would be very much appreciated if someone that is more familiar with the correct settings (and the wording) may be able to give me some clues to point me in the right direction.

Cheers

Paul