how can i connect local host to database

Depends on where the database or the database server is hosted. If that is on the same local host, then you can surely connect. Just pass the connection string, otherwise if the server is hosted on any other network then you first need to get the IP address to connect to that server at. 

 

You can get a few strings for your database server (you didn't mention which one you are interested in, SQL Server, MySQL or what?), anyways, you can get a connection string from: connectionstrings.com. Then use that string to connect to the server and get or update the data in the database.