Page History

1. In the page you want to change, click Edit. 
2. At the place on the page where you want the link to appear, paste the URL. Confluence automatically converts the URL to a link. 
3. If necessary, edit the resulting link text. (Use the Source Editor to edit the first or last character of link text.)
4. If necessary, edit the link address:
   1. Click the link text. A row of buttons appears.
   2. Click Edit. The Edit link dialog box appears. 
   3. Select Web link. Modify the address for the website. (Modifying the link text at this point might not work correctly.)
   4. Click Save. 

If For every link in which the website is external to the U.S. Government, you must add an exit disclaimer as described in How to create links to external sitesMarking Links as External to US Government. 

Also refer to Linking to from a Wiki Page from to a Wiki Page.