You cannot attach files due to the trust level of your account, please refer to my comment here on that: Community rules - #14 by Constantine
Before getting promoted to the next trust level according to the requirements in my comment you can use a workaround of uploading your file to a cloud storage and sharing a link here. If you feel like your file has any sensitive data in it, you can share the link via PM by clicking my avatar and starting a PM via Message button.