In AL you have the snippet treport that creates the basic structure of a report object. Creating a report is a 2 phase design:
Step 1: create the dataset with AL
Step 2: create the layout (Report Builder or Word)
To learn more about reports, start from here:
docs.microsoft.com/.../devenv-reports
Remember that you cannot modify existing reports, but in this case you need to clone the existing and then modify this copy.