Accpetance of the offer of employment

hi, may u plz help me sending a letter to the firm i want to join. they accepted me and offered me a position there and i want to replay stating my acceptance of the offer in a formal way. the HR manager sent me this letter:-

"Congratulations! I am pleased to inform you that post discussions and feedback from the panel, we hereby wish to make an offer as per the attachment. Please go through and request you to acknowledge by
15th August 2008. If you have any questions or need any clarifications, please feel free to do so"

Thank you in advance