You can adjust the size of tab control frame by using either of three methods as shown below.
First method by using Properties setting:
- Right click at Tab Control.
- Click Properties.
- Go to Appearance > edit Height and Width in Size part.

Another way to adjust the Tab Control frame's size is by:
- Right click the Tab Control.
- Click Fit Control to Pane and tab size will be fit to your screen size.

Or you also can manually drag tab frame to adjust the size.