You'll have to play around a bit with this code to get it working for you.
Database connection and data selection:
Dim Connection As New Data.OleDb.OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=YourDatabseName.mdb;")
Dim Command As New Data.OleDb.OleDbCommand("SELECT * FROM TableName", Connection)
Connection.Open()
Dim Reader As OleDbDataReader = Command.ExecuteReader
Do While Reader.Read()
Dim str1 As String = Reader.Item("Column1Name")
Dim str2 As String = Reader.Item("Column2Name")
Dim str3 As String = Reader.Item("Column3Name")
Loop
Connection.Close()
As for updating the treeview:
TreeView1.Nodes.Add(New TreeNode("NewNode"))
TreeView1.Nodes(0).Nodes.Add(New TreeNode("ChildNode"))
TreeView1.Nodes(0).Nodes.Add(New TreeNode("ChildNode"))
TreeView1.Nodes(0).Nodes(0).Nodes.Add(New TreeNode("ChildChildNode"))