How to create a web service for an existing application

Question

Hello, I am a new developer and I have been having a problem. I have created a database for employees on SQL Server Management Studios and have connected it to an application in C# using Visual Studios that allows me to add to and search my database for individual employees using either their ID, name, position, or salary. Now I want to create a web service that will allow me to do the same on a web browser. i have looked at other instructional videos and documents but all of them start from scratch. Thank you