Use the connection string in App.Config

[FastEddie]

I have a connection string named in my app.config file but I don't know how to reference it with code. For instance what do I put in the connection string for this code block?

Dim cnn As New OleDbConnection
        Dim cmd As New OleDbCommand
        Dim dr As OleDbDataReader
        cnn.ConnectionString = ""
        cmd = cnn.CreateCommand

My connection settings look like this

<connectionStrings>
        <add 
          name="BarCodeReader.My.MySettings.db4ConnectionString" 
          connectionString="Provider=Microsoft.Jet.OLEDB.4.0;Data Source=|DataDirectory|\db4.mdb"
          providerName="System.Data.OleDb" />
    </connectionStrings>