Follow these steps to insert a link in an email in Mozilla Thunderbird or Netscape:

When composing a message, press Ctrl-K (Windows, Linux) or Command-K (Mac). Alternatively, highlight the text that you would like to serve as the link and press the Ctrl-K shortcut key. Under Enter text to display for the link, enter the text you want to serve as the clickable link. Under Link Location, enter the URL address for the page you’d like to link to. It’s easiest to open the page in a browser window or tab, copy the URL from the address bar and paste it here. Select OK to place the link into your email. Complete the email message and send it as usual.