How do I program my keyless remote?

First it would help if you told us what year Xterra you own.

Second you might search since a lot of info is available. I searched in this forum and came up with the below link. Try it to start.

http://www.xterraownersclub.com/ubb/ultimatebb.php?ubb=get_topic;f=4;t=003061#000001