Skill Level: Easy

There are many ways to accomplish this task. Below are two robust and relatively easy guides to follow.

You will need to first install your favorite Linux distro and then start the guide. See here for how to install Ubuntu on the Intel NUC.

Install the OpenHAB Ubuntu Appliance for an Intel NUC

openHABian - Hassle-free openHAB Setup

Either of these processes will set up your NUC so it's dedicated to running openHAB. However please note that openHAB is very lightweight so it's probably a waste of resources to dedicate an entire PC to it, unless you have a very large home.