Greetings, Prof Aravind,
The CTAT components are, initially, empty <div> elements with CTAT-specific class attributes that you arrange on your student interface's HTML. The CTAT runtime code in ctat.min.js (that you include with a <script> tag in your HTML <head>) reads the document once the page is loaded and, for each <div> with a CTAT class (CTATTextInput, CTATButton, etc), invokes constructor code that dynamically adds actual HTML components (<input>, <button>, ...) as child elements of the original <div>s.
The code that usually invokes the CTAT runtime in ctat.min.js is in ctatloader.js (also included via a <script> tag in the HTML <head>). This separate JavaScript file tries to determine the LMS environment (is this invocation for OLI, edX, Tutorshop, no LMS, ...) in order to call the runtime initializer function initTutor() properly for that situation.
Hence in addition to the CSS files, you'll need to ensure that ctat.min.js is included and initTutor() is called on or after the onload event. See
this MDN page for info re: onload. Thanks!
Jonathan