Just your OS?
You would basically need to uninstall all your programs after moving all your games [that use a launcher (Steam,Origin,Uplay...)], your docs, pics, music, videos, downloads, emails... to another drive. Once that all done, you clone the current drive to the new drive.
Many SSD's come with cloning software. Samsungs is excellent for their SSD's and Macrium Reflect Free is as well AND works on all SSD's. Be warned you cannot easily go from an AHCI Sata drive to an NVME.