Well, I can't tell you all the hows because each barn is different. What I can
tell you is how I went about getting my feet wet in the horse world.
I had very little experience with horses, but decided I wanted to give working with them a try to see how I liked it. My experience up until that point was just a few trail rides here and there ( like as an excursion on a cruise, or around the ring at the fair type of thing). So, after college I moved from Louisiana to Montana to work on a dude ranch for a season. Best experience of my life! First-- it is Montana, the most beautiful place on earth. Second, I was surrounded by experts. I started out really small, mostly doing other ranch work( 95% of my job had nothing to do with horses, barns, trails, etc) with minimal horse contact. But, once I proved myself to be somewhat intelligent and capable, I was given more access.
That came in the form of handling some tack, feeding, CLEANING<-- lots and lots of stall/barn cleaning.
Then, I was able to move out onto the trails more with guests when they came to the ranch. By the end of the season, I was still a newbie-- but I had the "horse bug", and knew what direction I wanted to go, had learned some terminology, knew what to look for [somewhat] in regards to horse health [i.e. colic]. Just some things that only time and experience will lend you.
After that stint, I moved to Tennessee for a "real" job [ aka, the job that now
pays for my horse habit!], and volunteered at a barn that housed 27 Tennessee Walking Horses. I had a more clear/concrete description at this barn: feed 2x a day a mixture of hay/grain/supplements depending on the horse, water 2x/day, clean stalls, sweep common areas, lots and lots of hay stacking/rearranging, occasional trailer cleaning, tack room cleaning, spider web knocking down... anything that is associated with a barn. I did that for several months
NOW, I decided I wanted to take it up a notch about 6 months ago and invested in 1x1 lessons with a trainer a couple times a week. In addition to my lessons, I spend a lot of time in the barn helping out, feeding, organizing tack, feeding again, moving horses around the pasture(s) depending on the need, grooming horses, talking to newbies at the barn who are getting lessons and might be nervous, etc.
Everything is layered by experience. Every day I learn something new, whether through experiences, reading and online research or by talking to people more knowledgeable than myself. I wouldn't say you're unqualified, because we were all unqualified at one point-- but be prepared to muck stalls and not get much interaction with horses at first. You kind of need to "earn your stripes" so to speak, and you WANT to get that experience and knowledge before jumping in head first.
I went to Montana in 2009, so this has been a slow rolling progression of learning and gaining new experiences. Be patient, there's so much
to learn, give yourself time to absorb it.
Sorry, this turned out WAY longer than I anticipated! Hope it helps..