The first step is to clearly explain your needs. The more detailed and actionable the better. The more specific you are in describing your request the better the mentor match.
Give your mentorship request a clear title. Ideally you are able to explain what sector your business is in and the exact need for support.
Explain the challenge you are facing. What steps you have taken to try and address this challenge.
Explain what kind of support you think would be useful. Why will this help you address the challenges you face?