Open the link or the site in one window and copy the URL address.
When you write your article and choose a word or phrase you'd like to be contain your link highlight it by dragging your mouse over it as if you were going to copy it but instead "right click".
You should get a drop down menu with a spot to input your hyperlink. Paste the link you copied from the other window/site and hit ok.
That word or sentence in your article should now appear to be highlighted in blue. If the reader clicks on it they will be directed to the other site you want them to view.