How do you handle, the introduction of a concept and its use?
There are many ways to do this. Generally, you don't introduce it at all, you just have a character (or, say, a sign or something on a meditation center) state the concept.
Then you have somebody that is clueless about what it means ask about it, and somebody explain it, in the same simplistic terms (without a class) you would explain it to a novice. Think of it as the "one minute university" version, think of a professor (or meditation center manager) that is in something of a hurry and has one minute to say something. The average talking speed is 125 words per minute (faster in some people/regions/languages, slower in others) and the average reading speed is 200 words per minute.
Set that is your limit: A practiced person that knows what they are talking about has 125 words to explain "Buddha nature", then they gotta run. So they leave out nuances, and convey a general idea.
ONE ALTERNATIVE is to generate a conflict; take TWO people that know what they are talking about, friends or enemies, and have them argue about their interpretations of what Buddha Nature is. Arguments, by the nature of dialogue and the interest sustained by the thrust and parry, can be longer than a page, just make sure the arguments are "legitimate" and seem valid, nobody saying "You're wrong Jim, but do go on for five minutes."
With an argument you can introduce more underlying concepts and oddly enough when we hear arguments we will build an approximation of the "center" or average position, and develop our own notion of what "Buddha Nature" means.
SECOND ALTERNATIVE, the character wondering about Buddha Nature finds a pamphlet that explains it. Similar to the knowledgeable person, but not interactive, and the paragraph or two they read can be more formally crafted (it doesn't have to sound like something a live person would say off the top of their head). Still, keep it to 125 words.
THIRD ALTERNATIVE: You may not need to explain it all. If understanding Buddha Nature is not really relevant to the plot, and this understanding has no influence on any characters involved, then it is fine to mention it for realism but not necessary to explain what it is.
In this sense, it is background color. If I show a forest in fall, I can describe the colors of leaves without explaining why they get that way.
Experiencing or witnessing or reading things we don't understand is part of everyday life, and we just presume it means something. I don't know what the barristas are doing half the time, but I presume they aren't just dancing or making random motions behind the bar.
If a chef tastes some mixture they are making and nods, I don't know what they were testing for and found.
What matters is if the non-understood thing actually matters, either to the plot, or to character development. To be worth explaining, it must have some influence on their decisions or feelings, or lead to a discovery, or love, or a realization of betrayal, etc. It must be necessary and shape the story and/or character in some way, impossible without it. Even a subtle way, e.g. knowing what Buddha Nature is might help convince a Buddhist later to take a risk and provide aid.
If it is not worth explaining, it is still useful for the realism it contributes to, say, visiting a meditation center. As authors, our job is to assist the reader's imagination, and describing settings is a part of that, giving them a feel for where they are and what it feels like. Including elements that add to the atmosphere of the place, and how they may feel in the moment being there, but don't really matter beyond that.