The window with the text is called a “console” window. It should have the RawTherapee version in the title, does it? e.g. “RawTherapee 4.2.699 Console”
That console window should only appear if you set verbose=true in the options file. Edit the options file in a text editor and make sure verbose=false
Where to find the options file: File Paths - RawPedia
If your options file already has verbose=false then please show a screenshot of the whole RT window and of this console window, and also tell us exactly which RT version you’re using and where you got it from (the exact URL, don’t just say “from this forum”).
This page explains how to take screenshots:
http://rawpedia.rawtherapee.com/Forum