What region/nation are you discussing? In England, if a man made an annual income of less than five pounds a year, then he was legally required to own a longbow and practice with it. There were few other places in Europe where archery was so common among the general population. The local lord would have little to do with archery training for most of the population. A man started as a child playing with small "toy" bows, which got progressively larger as the child grew into a man. When he became an adult, he would be able to use the full-scale war bow. This village archery practice would have been done regardless of whether an active war was taking place, because it was important to have a pool of capable archers at all times in the even of war suddenly breaking out.

What sort of background is this young man from? If he's the son of some random village farmers, then he pretty much just has the bow, a long dagger, and a padded jacket. If his family was more wealthy freehold farmers, then he would be much better equipped, with a helmet, sword, buckler, and maybe some armor to go along with his bow. A yeoman archer might even have a horse, which means he draws more pay as a mounted archer. Someone this rich might even be in the position to command a company of other, poorer archers from the surrounding area.

In 1329 in England, the Hundred Years War had not yet begun, but that doesn't mean England was peaceful. Edward III has recently ascended to the throne, after the rather pathetic abdication of his weak father, Edward II. However, the real power behind the throne is the extremely unpopular Roger Mortimer. In one year, Edward III will have Mortimer executed and truly become the king he was destined to be. Edward III is a pretty good king to be a subject of, if you are a longbow archer and you want to make decent money by fighting. Edward III does a lot of fighting, and he's generally pretty good at it, so it's less likely that you'll die. There's the Hundred Years War, which begins in 1337, and then there's the perpetual fighting with Scotland.

During the Hundred years' war (I know it starts in 1337 but I would not think the system changed much), more than France and England, it was two very different ways to wage war that fought.

The French would generally not field archers but would favor professional mercenaries with crossbows (from Genoa) and would generally not field any archer or very few. Their strategy relied a lot on the very powerful mounted French nobles that would use shock tactics by launching big charges of armoured knights on the English weak points (generally there main aim was to rout the English archers by charging straight to them, locomotive style).

The English used the archers extensively, it was even their main asset and their whole strategy lied basically on them. In order to field the huge quantities of levy archers they needed for it, they had a law stating that every peasant in age to fight had to possess a long bow and be proficient with it. It meant that their whole adult male population were archers that were always ready to be levied if needed.

So to answer your question you would not join like you would join the army today. You were a peasant and an archer for most of your adult life providing you were male. You would then be called to arms by your king if needed and sent to wherever he needed you to be.

Meaning that in time of peace your lord would probably tell you to jog on and get back to harvesting your wheat before it spoils.

If you want to know more about the tactics of the time you can have a look into "Eward prince of Wales and Aquitaine: A biography of the Black Prince" by Richard Barber