There are two ways you can add hyperlinks to text.
The easiest way is to simply type an Internet address. For instance, type http://www.xtreeme.com, and press the “Space” key (note the “http://” part). The address you type automatically turns into a link. The same happens if you type just www.xtreeme.com. You can use this for email addresses as well! The editor will automatically turn anything it can recognize as an Internet or email address into a link.
Sometimes, you may want to create a link to an Internet or email address using some arbitrary text instead of the address it points to. Select text you want to convert to a link, and click the “Insert Link” button 
. This brings up the “Hyperlink” window.
Type the Internet address in the “URL” text box. If it is a link to a web page, it should contain the “http://” prefix. To create a clickable email address, type it with a “mailto:” prefix. Example: mailto:myaddress@mycompany.com
You can click the “Insert Field” button 
to insert a click-tracking link.
Below you may see the different kinds of links created in the message editor.
To insert a click-tracking link, click the “Insert Link” toolbar button 
, and then click the 
button next to the “URL” text box. Select a tracking link from the list.
To learn more, read this section: Using Click-Tracking.