Have you ever used DIVs? These allow you to divide your page with invisible boxes and you can style them to how you wish. So in your case, wrap the content with a DIV tag, and style its margin and width:
HTML:
<div style="width:200px; margin:auto;">
<p>Hello world.</p>
<p>Replace the content here as you wish. Notice that if the text is too big to fit on one line, it will automatically start a new one!</p>
</div>
Simple as!
You can even give it a "class", then it can be referred to separately. Dreamweaver lets you do that fairly easily. Try this:
- Highlight the page content you wish to be in the centre of the page
- Insert > Layout Objects > Div Tag
- Make sure "Wrap around selection" is selected, and click "New CSS Rule"
- Underneath "Choose a contextual selector type for your CSS rule", select "Class". Give it a name of "middle", and select "This document only". Click OK.
- Click on Box, then type in a width of your choice. In the Margin section, clear the "Same for all" check box, and select "auto" for left and right. Click on OK twice.
Have a look at the code it's produced and see if you can understand it. The advantage of using this method is that by simplying entering "middle" as a class for any div tag, it will be automatically assigned to the properties stated towards the top of the page.
One more thing... try to give a better subject for a thread. So instead of "little help", try "Centre section in Dreamweaver". That way, the right people will be able to look at just the title and know exactly what to do.