Kinda new here ^^ so here's what you gotta do :D
Paint a thin layer of your choice of pastel nail polish and let it dry ^^
Draw a thin streak in the middle ,using the medium colored nail polish and wait for it to dry 😊
Next , draw another streak below the medium colored nail polish and let it dry , don't worry if its messy , you'll eventually be using the nail art pen to go over the messed up parts ☺
Create your desired patterns with your black nail art pen and you're done ! 😀
Hope you like it !>< sorry if its not pretty or nice 😣 just sharing my ideas☺ Enjoy !