Hey @Nel6 and welcome to the Community.
Up to 6 weeks after your installation, you receive an email with instructions on how to register for your gift card. From there, you would choose which $100 gift card you would like to receive. You are also given the choice to either get a physical or electronic gift card.
Did you end up installing your Internet service?
Also, did you provide an email address to receive the promotion?
Let us know.