Samsung

I was told about the site mptrim.com. where you can download your own music and trim it down to 30-40 second clips to then upload to your phone. Is anyone familiar with this site? I'm alittle technologically challenged and could use a step by step walk through on this process. I tried to download a song to trim when it asks for a file name i'm not sure what to type in. Someone help if you can. Thanks