@arcadianadvocate: First you copy the URL of the site you want to link to from the address bar of your browser (the complete address, starting with "http"). Then you go to Manage>Posts and click the title of the post you want add the link into. If you use the visual post editor (there will be two rows of icons above it), you highlight the word or words that will act as the link, click the Link icon (row 1, icon 10), paste the URL in the box that opens, select Target "Open link in a new window",* click Insert, click Save. If you use the HTML post editor, you use this code:
<a href="URL" target="_blank">TEXT</a>
(where URL is the address of the site and TEXT the word or words that will act as a link).
* This is optional, but it's better to use it: this way one doesn't leave your blog when opening a link.
@freddiemaize: The way to paste code here is enclosing it in backticks (that's what produces the frame you see above).