Hi ng tian xin,
Several weeks ago, Adobe announced that it was retiring Adobe FormsCentral on July 28 2015. As such, we are no longer offering new subscriptions to FormsCentral. If you have Acrobat, you can use that to create PDF forms (you're welcome to try Acrobat for free for 30 days--see http://www.adobe.com/products/acrobat.html).
If you're interested, here's some background information about the retiring of FormsCentral: End of support | Adobe FormsCentral. (This document lists some alternatives to FormsCentral that you may want to check out in addition to Acrobat.)