You need portals and relationships for that.
Here's one possibility:
Add a third Table, Main with one calculation field, constOne. Enter the number 1 as the sole calculation term for constOne. Define a number field, one in each of your existing tables.
Define two relationships between Main and the other two tables:
Main::constOne = Table1::One
Main::constOne = Table2::One
Drag from constOne to One in the other table in while in Manage | database | Relationships. Then doubleclick the line linking the two tables this action creates to bring up a dialog box where you can select "Allow Creation of Records via this relationship for both Table1 and Table2. Then repeat for table 2.
Now you can set up a layout to NoData with your tab control and you can place a portal to table1 on one tab and a portal to table 2 on the other.
With these relationships and the "allow create..." option, you can create records in each table by entering data into the bottom blank row of either portal.
Appreciate the info I'll reads more about relationships and tables and try to implement it.