Journal referencing word 2010

Hello,

I am trying to include the url for referencing journal articles that I have accessed online. There is no option that seems to work for this. If I go on Manage sources- edit- select "journal article" from the drop down box - show all fields I then try typing the url in the relevant box. However, when I do this the url does not appear in my bibliography. I am using the vancouver referencing style downloaded onto Microsoft with vancouver.xsl .Any ideas on how to fix this? Many thanks in advance !