Generally there was nothing quite like the Witcher schools in medieval Europe, at least not with regard to fencing. Established, permanent schools weren't really a thing, but there were literary traditions of Fechtbucher or fencing books that proliferated certain fencing traditions. But we should be careful in their use, because some Fechtbucher were of dubious value without a teacher to interpret the book, and furthermore, Fechtbucher were as much an iteration of a particular literary tradition as they were an iteration of styles or approaches to fencing, and were directed at a subculture of dedicated fencing adherents, rather than just anyone who used a sword.

To get round to your question, generally an "absolute novice" would be relatively rare. Much of medieval athletic culture was enthusiastically amateur, and young kids, especially boys, would engage in a wide variety of martial play. Wrestling and climbing, throwing and shooting were omnipresent activities for youths of every class, the only difference being their access to particular equipment, eg a peasant boy might throw stones or learn to shoot a sling, where a rich boy might learn on javelins and shoot a crossbow. Fencing was considered an extension of wrestling, and kids would likely start fencing about as soon as they found a stick and swung it at their closest friend. This is all to say there were relatively consistent social encouragements for young boys to learn how to fight in whatever way their particular culture was expected to fight.

So learning how to sword fight could be as simple as finding the best fencer in your town, village, or city, and having them teach you. At fairs or market days you might be able to find a traveling fencing master who would be willing to teach you for a fee. If you were a member of a wealthy and important nobleman's household, you might have access to a live-in fencing tutor who might be able to give you something closer to a comprehensive education in whatever fencing philosophy he followed, or his lifelong bag of tricks he preferred. There is no consistency or coherence here, much of this would depend on luck and access to social networks that included fencing masters.

As it happens I have written about this a few times before.

This answer covers how one might hire a famous fencing master - in this case, the late 14th century Italian fencing master Fiore dei Liberi

And this one speculates on the physique of a knight, with more about the athletic culture.