The playback speed is very easy to change with a simple tap. You can control playback speed by going to a prayer and tapping on the icon that looks like either 1X, 1.3X, 1.6X, or 2X indicating playback speed.
If you can't locate the playback control then please watch the following brief videos walking you through the interface for iPhone, which works in a similar way on iPad, so that you can locate the speed control and other useful controls.