But there was no instructions anywhere that said Turn On .....NAS
You can create our own SD card if you have a PC or Mac.
Install a copy of Etcher
Then download the image file from here
Plug your target SD card into your PC (you can use a USB SD card adaptor)
Then fire up Etcher and point it at the image file you downloaded. Select the SD card and click on Flash.
Once installed in the B2 you will probably want to do a Web Upgrade to get the latest code.
Any SD above 8G will be OK. Class 10 will boot faster but otherwise not important.