Biographies and other pages on WikiTree are wiki, which means that anyone can easily edit them.
If you're logged in you will see "edit" links. These bring you to text editing boxes for making changes or additions.
Editing text doesn't require any special knowledge. It's all very easy. Most common formatting such as italics, bold, underline, and headlines, is available through the toolbar at the top of the editing box.
If you want to create a bulleted list, you can start each item with a * or # (the latter is for numbered bullet items).
To add links, use brackets [http://www.WikiTree.com/wiki/Adding_links like this]. (More help on links.)
For more advanced editing techniques, see this Wikipedia page on wikitext.