Entering and editing text in your topics in Help+Manual is very similar to working in a word processor. To edit a topic select the topic in the Table of Contents or Project Files section of the Project Explorer, then click inside the editing window to start editing.
The Write tab in the Ribbon provides direct access to all the tools you need while you are editing. The only group inside this section that may be unfamiliar to word processor users is the Insert group, which contains special tools and objects used in help authoring projects.
Use Styles (Quick Start Tutorial)