In general, when something is "prepared" in the Bible it means that it is in the proper spiritual order, which happens when our hearts and minds are open to the Lord's love and wisdom, and when our internal beliefs and good desires guide our actions. In a sense, this comes on two levels. There are times when people prepare themselves or prepare things; this refers to us making an ongoing effort to bring ourselves into spiritual order. There are other times when the Lord prepares something; this represents grace, by which the Lord can reach into us and elevate us, either to a purer state of spiritual order or ultimately to heaven.