In order to get to the next part which you will need access to the setting menu, you have to do this part.

Click the "untitled" tab at the top right.

To select a theme, select the customize appearance tab on the top right hand side, listed under "open untitled"

Select themes. ( Top left )

There's a drop down menu here which you can select the option for "FREE THEMES". Then just pick one and that's your blog post set.