Can we use our own forms we have now for clients to go to your site and fill in?

If your forms are fillable PDF forms from Adobe FormsCentral, then you can import them to your JotForm account: https://www.jotform.com/help/340-How-to-Import-Adobe-FormsCentral-PDF-Forms-to-JotForm 

Otherwise, you will need to create them from the scratch using our form builder. Let us know if you need more help.