Click on the Add button as if you were going to add a person and there is a delete option within the menu. There are also options there for disconnecting or connecting to other people in the tree, which you may have to do. If you have a big tree with a lot of people you need to consolidate properly, it will take a lot of concentration and attention to detail. I know that from personal experience. It's taken a lot of work to get a tree with 10,000 names with no repeats(there could easily be some).