Simply replace the unfilled areas such as "[]" and "[date]" with your information.
To whom this may concern,
This is to inform you that [name of company] is now open and is located at [address].
Our store offers a complete and diverse line of [product description]. Enclosed, for your review, is a partial list of the items we currently have available.
We hope that you will come and visit us soon.
All the best,
[name]