The best way to add patterns to Sketch is downloading a pattern from subtle patterns and then add the .png file to the background of the selected element. They have listed more than 450+ patterns including dot patterns, stripe patterns, and icon patterns as well.
To add downloaded pattern to an element you have to do is Select the element > Fill > Pattern Fill > Choose the pattern image you’ve downloaded. Done! It’s simple as that.
We have also collected 3 awesome free Sketch patterns for you.