Hi there JamesPeladeau,
As Aleszandro143 already suggested, you need to use some cloning software. Though, keep in mind that in case your current drive is failing, you can consider performing a clean install as well.
Apart from that, you need to attach the drive to your system either internally(if you have a desktop computer) or externally(in case you have a laptop).
In order to attach it internally, you will need SATA + power cable. In case you want to attach it externally, you will need SATA to USB cable + external power source.
Cheers,
D_Know_WD