Apple has a new version of macOS called Monterey that you’ll find in the Software Update pane in System Preferences. However, if you want to update the old-fashioned way, we’ll show you what you need to create a bootable macOS Monterey installation drive. (Editor’s note: These instructions are for the officially released version of macOS Monterey, not a beta. It was performed on a Mac running macOS 11 Big Sur.)
Get an external drive and maybe an adapter
The macOS Monterey installer software is over 12GB, so you need a USB external drive that can hold that much data. The drive can be a thumb drive, hard drive, or SSD.
Read more at Macworld.com