Use the built-in editor
Site Builder's TinyMCE editor (see image below) functions much like a typical word document editor. (There are some exceptions: you cannot change the size, type and colour of the font, you cannot highlight text, there is no "underline" function, there is no line spacing option).
*Note: The TinyMCE editor has a "Paste as plain text" function. When checked, any text you paste into the content area will appear as plain text (text already formatted will lose it's formatting). When unchecked, any text you paste will appear exactly as you copied it (formatted text will keep it's formatting).