Login to your account as admin
Click The following link: Setup Costi role which will pre-configure the CloudFormation values for you.
Alternatively use the following link: Setup Costi Read Only which will only give the Costi role read permission.
Click 'Next' three times.
Mark the "I acknowledge that AWS CloudFormation might create IAM resources with custom names." check box.
Click the "Create" button.
That's it, you're all done!