how to whitelabel my heroku app on sendgrid?

First i must say i have searched on here high and low and read all of sendgrids and heroku help pages for how to do this and this is my last resort.

I have done the rails tutorial by michael hartl and can not implement the email sign up confirmation. the final step is to whitelabel my sendgrid account.

sendgrid gives some information that I must add to my heroku app but i am lost at this point as i dont know where to enter it and have no idea what exactly i am doing. i am simply following this stage blindly.

the instructions it gives me are

DNS Record information for sending your email with your whitelabel. Copy the following DNS Records into your hosting provider. If you have questions please refer to our documentation.

then it gives me CNAME records with HOST and DATA. I am lost as to where i should enter this information on heroku. I am sorry that this question seems vague but i have never been so lost in asking a question on here so please let me know if there is any further information i can provide to clarify my question.

how to i whitelabel my heroku app on sendgrid?