Support system with multiple client sites


we are getting setup with you guys! so far everything is working great! Had a quick question: We have installed the support system on our site. We host multiple sites for our clients, we build their sites and manage the admin side of things. All our clients are not on multisite but using WP individual installs. How do I go about linking our support system into their sites if they want to submit a ticket? We will have it installed on our main company website. Just thought it would be really cool if they could submit a ticket directly from their admin area of their site