It is very easy. If you want to place a link then simply click on the tool bar button 'external link' which is at the top right corner of the answering window. A blue window will appear at the right bottom side which will ask 'External Link Name'. Give any meaningful name of your link and give the web address in the 'External Link URL' and click on submit. When you will answer the question by clicking on 'Answer Now!' then you link will be highlighted blue in the answer.