You do not "enter" a key into the software.
: A single subscription typically allows you to be signed in on multiple computers, but you can only have the software active on two at any given time. SketchUp Community SketchUp plans and pricing: Compare features & subscribe Sketchup Pro 2023 License Key
It is important to clarify that Trimble, the developer of SketchUp, transitioned to a several years ago. As of SketchUp Pro 2023, traditional "Classic" perpetual license keys (serial numbers and authorization codes) are no longer sold or issued for new versions. You do not "enter" a key into the software