Hi Vignesh,
The script function ClipboardPaste() will work in a Windows Client of Rocket MX Desktop (fka LegaSuite GUI) but not in Rocket MX Web.
For a 'regular' paste you can enable the right mouse menu, setting it to "standard", like this:
which enabledsthe browser's default right-mouse menu.
In the web client or when performing a live test test, this will give you a right-mouse menu with a 'Paste' option on the TextArea field for pasting, and also Ctrl-V will work:

Hope this helps,
Regards,
Roger.