You can align objects and text in Dreamweaver using the "align" commands, among other things;
Align text
You align text on the page using the Property inspector or the Text > Align submenu. You can center any element on a page using the Text > Align > Center command.
Align text on a page - Select the text you want to align or simply insert the pointer at the beginning of the text.
- Click an alignment option (Left, Right, or Center) in the Property inspector, or select Text > Align and select an alignment command.
Center page elements - Select the element (image, plug‑in, table, or other page element) you want to center.
- Select Text > Align > Center.
- Note: You can align and center complete blocks of text; you cannot align or center part of a heading or part of a paragraph.
The size of the images you use depends on what you are trying to achieve, and how fast you want your site to be. Large images take longer to load.
Here is the complete Dreamweaver help;
http://help.adobe.com/en_US/Dreamwea...ing/index.html
EDIT: Just a tip here, if you are learning this from scratch, then install a server on your local machine, and try everything out there. This will save you time and frustration. This server will run more or less anything that runs on the web;
http://www.wampserver.com/
<http://www.wampserver.com/>
as will this;
http://www.apachefriends.org/en/xampp-windows.html
<http://www.apachefriends.org/en/xampp-windows.html>
Regards....Mike Connor