You can add links to plain text and HTML messages.

To see how to do so for each type of message, see below.

Plain Text Messages

To add a link to a plain text message, simply enter the full URL:

Be sure to include the http:// part at the beginning.

It won’t look clickable in your account, but when the message is sent most recipients’ email programs will make it clickable for them.

In order for links to be clickable for subscribers using the AOL program (as opposed to AOL webmail), HTML would need to be used.

For instance, if you’d like for this to be clickable:

http://www.aweber.com

… you’ll need to type the following into your plain text message:

http://www.aweber.com

Because the HTML will appear in most other email applications, you’ll want to consider this option only if you have a high concentration of AOL subscribers.

HTML Messages:

To add a link to an HTML message, highlight the text that you want to make clickable by clicking and dragging your mouse over it.

Click the “Insert/Edit a Hyperlink” icon in the HTML editor in the toolbar near the top of the box.

This brings up a popup window:

Type the address where your image is located online into the “Address” box and click “OK.”

source : Aweber.com