The buttons on the toolbar along the top of the viewer allow you to edit the tree.
Click on a node in the tree viewer to select the node and its clade. Double-click the node to collapse/un-collapse the clade in the view. Once you have selected a clade in the view, you can edit it using the following toolbar buttons:
In version 9 onwards, the toolbar also contains a Search box that allows you to search for particular tip labels. If a match is found, this tip is displayed on the tree and all other tips are greyed out. If you wish to search by a ﬁeld that is not currently displayed on a tip label, you need to change the ﬁeld under Show Tip Labels ﬁrst.