Before you can hyperlink you must create text to display. Once you've typed the text, you must select the text you want to use as the "display text". In Moodle you can insert a hyper-link by finding these icons and clicking on the connected chain or you can use Control K / Command K to open the hyperlink dialog box.
The following dialog box will open:
At this point you will enter the Link URL in the appropriate box. The next step is crucial so that your information opens in a new Internet Window while preserving your current Window. Use the drop down box to move the Target selection from "Open in this window/frame" to "Open in new window". Your final step is to select the "Insert" command.
By following these steps you will allow your user to open your content in a new window preserving whatever they have on their current window (such as e-mail or Moodle).
Below is a video tutorial. The hyper-linking portion goes pretty quick and it appears it is on an older version of Moodle. I hope to make my own tutorial video next time to show you on the most current version of Moodle.