Tap and hold on the first bar and drag a finger across the area of the song you would like to select.
A menu will appear that will let you choose from Cut, Copy, Delete and Insert space.

CUT - the selected area is removed, moving the remaining part of the chord progression back.
COPY - will save the content of the selected area to the clipboard.
DELETE - will clear the content of the selected cells without removing them.
INSERT SPACE - will insert empty space in the length of your selection
To PASTE it, double tap at the location you would like those chords and select Paste.