If you're using "Alexa Hosted," Alexa is hosting the Lambda and an S3 bucket for you as an IAM user on an account owned by Alexa. The Lambda is the "Code" tab in the developer console for your skill. In the lower right corner of that tab you'll find links to access the S3 and CloudWatch consoles for the AWS IAM identity attached to that skill.
You cannot access the Lambda console directly because the permissions for that IAM user are pretty tightly locked down.
Your best bet is to keep it in a .env file and use the dotenv node module.