Have a look in the System.Data namespace, there are a whole bunch of classes in there for dealing with databases.
You can also download connectors from Oracle for Oracle and MySQL
You then configure the connections for the appropriate database
http://www.connectionstrings.com/[
^]
Visit MSDN there are some good intro videos there to get you started.
http://msdn.microsoft.com/en-gb/vcsharp/bb798022.aspx[
^]
Here is a beginners article on CP about the subject which may also be worth a read.
Beginners guide to accessing SQL Server through C#[
^]