How to communicate rest api with SQL Server?

I'm developing an application with xamarin forms. I have created a rest api web to communicate the application with the server. Now I need to save data in SQL Server and I do not know how to do it.

What do I use to connect the backend (rest api) with a SQL Server?

I have looked at Entity Framework but in each Microsoft manual it says one thing and I do not see anything clear..

I really need help