Using the Tag Properties feature, you can easily apply different styles and change properties of selected elements. Please try to insert bold, italic or underlined text and after that put cursor to this text. You will see the tags. You can also try to apply HTML code sourcing for numbered list or any other element.
As for Blog module as I remember you can modify HTML code for post in post managing section. At the bottom of post window you should find HTML switcher next to draw pencil.