Install Pokemon: Black ROM (NDS) in the NDS emulator is a procedure that will help you to install all the ROMS of Nintendo DS games. Install Pokemon: Black ROM (NDS) for NDS Emulator (WinDS Pro)
There we explain you in a simple way how to complete the process step by step.
If not, it means that at some point you have selected another folder. Normally it is in the download folder that is selected by default when downloading a file.