Scenario:
"I would like my visitors to be able to search my site, but there is no search.php file or anything like that. What do I need to do?"
Solution:
Nucleus comes with a built in search function. Simply put the below code in your skin where you want your search box to show up.
<%searchform%>
Original forum thread (thanks, admun!):
http://forum.nucleuscms.org/viewtopic.php?t=4097
Further reading:
Not sure what a skin is? Here is another FAQ article which may help:
What is the difference between a skin and a template?