You enter the basic content for all pages on the site in the same way. You will be presented with a text area in which to type your words. The text will "wrap" around from line to line, and a scroll bar will appear when necessary. Press the Enter key only when you really want to start a new line, otherwise just let the text wrap automatically. Press the Enter key twice to get an empty line between paragraphs.
The text is not set in concrete once you have entered it — you can go back and delete, change or add extra content at any time. You may also use "copy and paste" to get some of your content from another document, but the formatting codes in a word-processed file will not be carried over — only the words themselves. The layout of a web page is managed automatically by the web browser.
The Site Builder is not a "wysiwyg" editing system like a word processor, but it does support a few simple formatting options: centred headings, bold and italic text, and tabulated lists. To see how to use them, see the Help file about simple text formatting.