To add Keywords Meta tags in Dreamweaver you click the arrow at the top right of the Objects palette and choose Head from the little pop-up menu, since Meta tags are inserted into the Head of an html document.

Or go to the Insert menu and choose Head>Keywords

Choose the key symbol from the palette to access the Keywords dialogue box. Then type a list of words that you expect a prospective browser might type into a search engine. Choose carefully and preferably no more than 10 to 15 words. Include likely misspellings. Brand names are debatable!

If someone does find you through a keyword, some search engines will display a description of your site to inform the user before they click through to your site. This description will usually be whatever you type into the dialogue box that you get when you click the symbol of a page with a speech bubble coming out of it. If you do not add this meta tag, a search engine won't display a coherent description but will instead just rattle off the first words it finds on the site (Google does this anyway). Keep descriptions short and avoid errors in spelling or grammar that deter prospective audience.