Simply replace the unfilled areas such as "__" and "_[date]_" with your information.
My name is [Name] and I am the [position] of the [Club/Association]. We are an organization that is dedicated to [club purpose]. We provide [services] and [additional services] to [recipients of service].
[Referring Party] gave me your name as someone who may be interested in our group. I understand that you [qualification]. I would like to invite you to join our [club/association]. I have taken the liberty of enclosing our information pamphlets. Please take some time to look over them. Also, I would like to invite you to attend our meeting on [date] at [time] located at [location]. This will give you an opportunity to meet other members and decide if you would like to join.
Let me know if I can answer any of your questions.