[Help] Planning to repurpose an old pen for a garden but....

Sorry its long, i like to get side tracked. Big help question is at the bottom, backstory and a little big of explanation to get a feel for the space at the top.

I didn't want to make the title too long. I moved into an old house to be a roommate for someone. She bought this house and fenced in part of it as a "parking area" sort of thing. The other side of the fence is also her property. When i finally unpacked everything i wanted to go look at the rest of the land, it was pretty grassy and is often used by guests to park in since the fenced area is pretty small. There is an old pen thats completely overgrown that looks like it was maybe used for chickens way back when. There are tree branches and all sorts of fauna growing in there (and an old toilet for some bizarre reason...). The posts are still intact and parts of the fence will need to be removed and replaced.

Now on to the help... I have done some major landscaping with my dad years ago to plant a large garden for my mom in the front of their house. Ive built raised gardens and everything, and got bags of specially formulated soil (Bricko Farms, Augusta, GA) from a local place that has great soil. Putting it in straight from the bag meant i didn't need to till the soil, especially since it was a 4x12 box. I did all of that by hand. Back with my moms huge garden, my dad had a tiller and used that, we covered it with weed barrier paper stuff, dirt, then mulch. My father has long since gotten rid of that tiller and has no interest or energy to help with this seeing as how he's the sole provider for a 5 person household.

I love veggie gardens. I want to know the bet way to go about "tilling" a space thats 6x20 (or bigger, i don't have an exact measurement there, but its bigger than my little boxes). Obviously ill need to get the big lawn trash (and the toilet. Or ill turn it into some sort of water thing. or a flower pot just for comedic effect) out of there first. But what does one do with a plot that big when you really have a shovel, your hands, and a stupidly determined attitude?

Edit: I are gud at Inglesh