Move checkbox in comment form

Greetings,
I’m trying to figure out how to modify the comment form on my website, https://www.ajharbison.com. Currently, the checkbox for “Notify me of follow-up comments by email” is right next to the “Post Comment” button (you can see an example here: https://ajharbison.com/blog/2016/04/illomusicfriday-4116-wisdom/). I’d like to put a space or two between the button and the checkbox, so that the checkbox is on the next line down (the way that the second checkbox is), but I haven’t been able to figure out how to do this. Can someone please help? Thanks!