Edit over functionality is available in the Ball-by-ball section of the Scoresheet. 

Highlighted Feature:

(1) - To Edit Over, tap on the “pencil” icon next to the Over heading.

(2) - To change the bowler for the entire over, tap on Bowler and choose from Selected Team players.

If multiple bowlers were involved in the over, for e.g. if a bowler was replaced mid-over due to injury, the Edit Over functionality won't allow you to change the bowler for the entire over. In such a case, using Edit Ball functionality is recommended.