In order to prevent charges to your account we recommend cleaning up the infrastructure that was created. If you plan to keep things running so you can examine the workshop a bit more please remember to do the cleanup when you are done. It is very easy to leave things running in an AWS account, forget about it, and then accrue charges.
In the AWS console, go to CloudFormation, click ModernizationWorkshop-EKS stack and then Delete. You do not need to choose the stacks for the workshop with the Nested tag, they will automatically be deleted as the ModernizationWorkshop-EKS stack is.
This process will take 15-30 minutes, to be sure to verify that none of the ModernizationWorkshop-EKS stacks are listed in CloudFormation and you are done.
You have a 15 day trial, so keep using it to monitor and manage your infrastructure and applications.
Here are some additional resources to checkout: