You can reveal Form using any element on page (eg. button, link or any media). Just add to HTML of this element special class nksub_trigger_element like this:

<a href="#" class="nksub_trigger_element">Press me</a>

Plugin script will attach opening function to any element with this class if it finds such.

Also you can add class from plugin main script. Let’s for example make all links to open form. Add this snippet at the very beginning of ninja-contact-form.min.js:

jQuery(function($) { // on DOM ready

Tip for menus

In WordPress on Appearance/Menus page click Screen Options in upper right corner and choose CSS classes in Show advanced menu properties. Then edit menu item and add nksub_trigger_element class.