Hi Buronya Kofi,

You could set the ConnectionString(What I marked as green could be changed by yourself ) in the appsettings.json like below:

"ConnectionStrings": {
    "DefaultConnection": "Server=(localdb)\\mssqllocaldb;Database=YourDatabaseName;Trusted_Connection=True;MultipleActiveResultSets=true"
  }

And get the connnection string like below:

services.AddDbContext<YourDbContext>(options =>
                    options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));

Reference:

https://docs.microsoft.com/en-us/aspnet/core/tutorials/first-mvc-app/working-with-sql?view=aspnetcore-3.1&tabs=visual-studio

Best Regards,

Rena