Hi Marianne,
It depends which link you want to create.
for example if you wish to create link to external site, you need to do the following:
a. create URL iView that points to that site.
b. if the site is doesn't allow to render in iFrame you need to change the "launch in new window" attribute of that iView to "Launch in new window".or else it will not work.
c. add your iView to page/role.
d. assign the role to the user / group.
if you want a link to an internal / existing page/iview you need to find that iView/page in the portal content (under content administration) and do steps c and d.
BR,
Saar