You need to make sure that no one in your house is using bit torrent or downloading copyrighted material illegally. Once you have done that, it is probably best to ignore the subpoena. These things usually don't turn into anything and a lien can only be put on your home if you are actually sued and the Plaintiff obtains a judgment.
If you actually get served with an Amended Complaint then you really may want to sit down with an attorney.
You can reach Harkess & Salter LLC at (303) 531-5380 or info@Harkess-Salter.com. Stephen Harkess is an attorney licensed in the state and federal courts of Colorado. This answer is for general information only and does not create an attorney client relationship between Stephen Harkess or Harkess & Salter LLC and any person. You should schedule a consultation with an attorney to discuss the specifics of your legal issues.