New laptop

I have just replaced my laptop, what do I have to do to transfer my Avast protection?

Have you taken a look at this support webpage?
https://support.avast.com/en-us/article/270/

Also to add, (If the Laptop is new)
Many new laptops come with an Anti Virus “Pre-Installed” and if not Avast, needs to be removed using the Venders Uninstall Utility BEFORE installing Avast on the machine.