Square Space is a "Do it Yourself" type tool, so for things like this it requires you to know how to do some coding work, know CSS to make things look better, etc.
The above video show you how to connect your Square Space web site to Spark to automatically add the lead to Spark.
I always recommend, for best results to use a professional martial arts specific web design company, it will pay for itself, and save you a lot of headaches if you are not a designer/programmer.
Ignite offers free websites (and are amazing!), when you are ready to take it to the next level in results.