Sign up form on website opens a new tab after sign up

Sign up form on website opens a new tab after sign up

I am having problems with Zoho campaigns, everytime I fill out my sign up form on my website it opens up a new tab I am currently using Zoho campaigns via the API, my website is www.prepfitapp.com, when you choose a category it gives you a sign up form after signing up it opens a new tab I want it to stay on the same page.