iOS How to show FileMerge in full window

I am using git with FileMerge to diff my source, but FileMerge always show in a window, not so clear.
I want to it can show in full window size, what can I do?

KoolStar said:

I would assume you click the Green Plus in the upper left corner of the application. Assuming thats what you mean.

Click to expand...

That doesn't work!
Please check screes as below.