Scroll to a letter your child is struggling to form and encourage them to follow it with their finger on the screen. If there are lots of letters they are forming in interesting ways, focus on 1 or 2 at a time and practice forming them using big movements outside, in flour, with chalk, or big bits of paper or with a paintbrush, before writing them smaller on paper!
https://www.youtube.com/watch?v=2NQ6uS8blwY