How to promote a software product

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C#

Dear Friends hope you all are fine and well.
Dear friends I need Your ideas in How to Promote my Developed Windows Application Software (Hospital Management System) Currently I have 43+ Clients or Hospitals in all around the country.

I started development of Hospital Management System in year 2011 in C# Windows Form + SQL Server, due to development I learned too much that have I can Developed a success software and then modification of system and maintenance etc.

1. I am taking project of Each hospital
2. Then installing my HMS in client's Hospital
3. Software Users training (Info Desk, Laboratory, Pharmacy and Doctors etc.)
4. After that they pay me Monthly fee for Maintenance, support, features modifications/addition in system.

My services go well...
but it's gone through me not a company.

please share business ideas with me to promote my software product and make a company for large services to more than 100 clients.

thanks in advance Dear Friends.

What I have tried:

How I can promote my software to find more clients?
how to make large my services in Country?
Thanks