Create the Main Layout Table
Insert a Table:
To insert a table with the layout tab selected click the insert table button on the panel:

At the insert a table dialog box fill in the following parameters:
Rows: 3
Columns: 2
Width: Leave blank
Border: 0
Cell Padding: 20
Cell Spacing: 0
Click OK to close the Table dialog box.
With the table still selected use your Properties inspector to:
Assign Table ID: mainTable
Align: Center