AWS SSM State Manager

Hello.

Creating an association requires the permission "ssm:CreateAssociation".
I think you will also need policies related to associations such as "UpdateAssociation" and "ListInstanceAssociations".
https://docs.aws.amazon.com/service-authorization/latest/reference/list_awssystemsmanager.html

You can edit the IAM policy used by an IAM user by following the steps in the document below.
https://docs.aws.amazon.com/IAM/latest/UserGuide/access_policies_manage-edit.html