The unPoster PAR window will automatically open the RAR window when the PAR window is done checking/fixing RAR files. When the RAR window is done, you can find the files it extracted in the folder named Extracted_Files inside the same folder where you have the RAR files.
You can also use the RAR window in “stand-alone” mode to extract files from RAR archives that you have downloaded with other programs. To do so, follow the instructions on this page.