It is the email you need to include in your stage 2 submission. I am not aware anything else is sent.
Print the email as PDF or something like that.
Another confusion you may experience is that in the list of documents to submit at TLS (during biometrics), the endorsement letter is not even mentioned.
You will need to submit it as “additional document”.
Per Home Office guidelines, your endorsement letter is the only document you should need to submit but I guess they have not updated their process.
Congratulations on your endorsement.