Which CDK class or function can be used to set the program source for CodeDeploy?

Hi，I want to use CDK to implement the process of operating CodeDeploy on the management console, and use CodeDeploy to deploy the program to a specified EC2 instance, but I can't find a definition of where the program is stored? For example, if my program data is on S3, how do I specify it?

const codedeployApp = new codedeploy.ServerApplication
const deploymentGroup = new codedeploy.ServerDeploymentGroup
const deploymentConfig = new codedeploy.ServerDeploymentConfig

I didn't find any settings for storage locations in the three classes above.

Also, is there a setting that can replace the contents of the AppSpec.yml?

Thanks for help.