Connection To Database With Name And Password

I want to allow access to a database from another computer via tcp/ip connection.

When i use Windows authentication, this works if access from the same Windows account name; it is not necessary to supply any UserID or something else. But how to authorize access from another windows user account?

When i don't use  Windows authentication ( SqlConnectionStringBuilder.IntegratedSecurity=false in C#) i never succeed to access to the database even on the pc where the database is. I created a login+password+user using code like

command.CommandText = String.Format( "CREATE LOGIN {0} WITH PASSWORD='{1}';", login, password );
command.ExecuteNonQuery();
command.CommandText = String.Format( "CREATE USER {0} FOR LOGIN {1};", userName, login );
command.ExecuteNonQuery();

but how to use these Login, user, password ? What i'd like to do is simple: allow access to my DB by supplying a Name and a Password.

I use VS express2014, C#, .net 4.x and VS CE 2013, Windows 8.1&7