Having Trouble Understanding The Process Of Getting Information From Access Database.How Do I Fill Combobox With Column From Database. Do I Use Dataadapter Or Datareader?

In general, using a DataReader can have advantages over using a DataAdapter. But for populating a ComboBox I would recommend you to use the DataAdapter.

Some suggestion for you in the comments:

private void Form1_Load(object sender, EventArgs e)
{
    comboBox1.DataSource = LoadDataTable("Database");
    comboBox1.DisplayMember = "ProductDescription";
}

// split your database-code into separate methods that don't
// access Form-members:
private void DataTable LoadDataTable(string tableName)
{
   // declare variables where you need them, not at the top of a method
   // (removed from here)

   try
   {
      string connection = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=Database.mdb";
      string sql = "Select * FROM " + tableName;

      // put everything Db***** (Connections, Commands, DataAdapter..)
      // in using(...)-blocks:
      using (var dbConn = new OleDbConnection(connection))
      using (var dbCmd = new OleDbCommand(sql, dbConn))
      using (var dbAdapter = new OleDbDataAdapter())
      {
          // a DataAdapter will open the connection automatically for you
          // (dbConn.Open() removed)
 
          // you only need a DataTable, not a whole DataSet:
          DataTable dt = new DataTable(tableName);
                
          dbAdapter.SelectCommand = dbCmd;
          dbAdapter.Fill(dt);

          return dt;
      } 
      // the connection will be closed here automatically
      // due to the effect of the using-block
      // (conn.Close() removed)
   }
   catch (Exception exc)
   {
       MessageBox.Show("Error: " + exc);
       
       // if you catch an exception and you don't do anything to deal
       // with the error (remedy it), then re-throw it:
       throw;
   }
}

As you might have recognized, the method LoadDataTable(..) now allows you to use it for any table in your database: Just give it the name of the table as an argument and you get a DataTable returned. So you can re-use it for other ComboBoxes or completely different purposes than binding to some control.