You can attach the AWSApplicationMigrationSSMAccess
policy to your IAM
identities.
This policy allows Amazon SSM operations required to use AWS Application Migration Service (AWS MGN) to run SSM documents post migration of source servers. Attach this policy to your users or roles. This policy is only intended to be used for the AWS MGN console.
Permissions details
To view the policy permission details see AWSApplicationMigrationSSMAccess in the AWS Managed Policy Reference Guide.