Edit, Write, Save is the simple cycle that you use to edit a page in Google Sites.
When you are editing the page, you will see a toolbar for formatting the text and laying out the page. (I've split it in two to make it easier to see on the page.)
The 'Edit - Write - Save' cycle for working in a wiki.
Image excerpted from "Wikis in Plain English" by CommonCraft
Left
Right
From here you can select the font, the size, colour, bold, indents, bullets, etc.
The Link (more info) option allows the creation of links to new pages, existing pages and to other websites.
The Format dropdown menu also allows you to add heading styles and align the text. Please use heading styles where appropriate rather than adding bold and increasing the font size manually. This increases the readability for people who need to use screen readers and it also makes your job easier!
The Table menu is for adding tables (!) and the Layout menu lets you change the page from 1 column to 2 columns.