In your cPanel, go to Mail > Autoresponders.
Click on Add AutoResponder.
Fill out the form with:
Email: enter the account name and choose the right domain
Hint: If you do not create a forwarder or email account with the same address as this auto responder, mail sent to this autoresponder will only be handled by the autoresponder before it is discarded.
From: You can type in your account address or any other but if you put a bad address or just a name, it will likely get tagged as spam and they may not see it. Use %from% to insert the sender's address.
Subject: You can put Re: %subject% as in a usual reply-to or your own Subject such as "On Vacation"
Character Set: US-Ascii for English or choose a different set for other languages if needed.
HTML Message: Check the box to send as an HTML message. This will allow you to use HTML codes in your message.
Body: Type in your message including any html tags you want to use. You can design it in a web design program then view and copy the source to paste in here. The html tags are not necessary.
Click on Create/Modify to finish. Send a message to the address to test. If you have any further questions support ticket.