You must activate your product within 30 days after you first installed and launched your SOLIDWORKS product. (Users working with an evaluation license equipped with product activation will have different timing requirements for the activation step).
If you do not activate your product by the 30th day after you first installed and launched your SOLIDWORKS product, it will stop working until you activate it.
You can move your software from your current computer to a new computer, open SOLIDWORKS then use the Help > Transfer License feature.
This feature deactivates the product on your current machine so it can be reactivated on the new machine. You then go to the new computer, install SOLIDWORKS then start it and select Help > Activate to proceed with the activation process.