You will need software with which you can play audio/video files and use your foot pedal to start, stop and rewind so you can transcribe them.
Express Scribe, which is free, is one program a lot of people use.The web site for Express Scribe is http://www.nch.com.au/scribe.
Two other free programs you can use to play audio files are FTR Player and The Record Player, from http://www.fortherecord.com. The Record Player also plays video files.