Then whatever Monster is using to drive the text box is not iPad compatible, and you won't be able to paste into it.
I don't use Monster, but look around in your user settings or preferences (if there are any) and see if you can choose a different text editor. Choose Basic or HTML if possible. The advanced editors are sometimes driven by plugins/extentions not available for the iPad.
If Monster will take a file upload instead, you might give iCab Mobile a try. You have to use Open In to copy the file to iCab Mobile, but once it is there you may be able to use the normal Choose File and Upload File buttons on a website. Some work. Some don't.