How to send SNS notification after cloud formation is completed?

You cannot specify notification ARNs via a CloudFormation template itself. You can specify them if you use the console to create the stack creation. But you cannot use the console to update the ARNs once the stack has been created. You can, however, use aws-cli to update the stack with notifications ARNs once it has been created, eg:

aws cloudformation update-stack --stack-name stack-name --use-previous-template --notification-arns "arn:aws:sns:us-east-1:${ACCOUNT_ID}:${TOPIC_NAME}"

Replace the variable ${VARIABLE} with the literal values from your account.

When create resources using a CF template there is an Advanced section of the Options menu. From there you can set Notification options using SNS and Topics.

When you start the CF process you can also view the status and importantly where the template might have failed.