200 square metres of turf is a lot. I can turf but it is hard work.
You will need to spray the entire area with glyphosate weed killer, buy the stuff to dilute. Let it do it's work, this may take a couple of weeks.
Next remove large stones and any rubble etc, there may be slabs hiding beneath and these will need to come out.
Level the ground properly, use a line and stakes to do this.
When you are satisfied it's pretty level consolidate the earth by trampling on it; I use a short scaffold board and jump on that.
Scatter a fine sprinkling of growmore on the area, it will help feed the lawn and attract roots to the soil.
Select your turf, use a proper turf merchant, the chains sell manky stuff for 2x the price. If it is going to take some stick,, I'd opt for meadow turf, it is hardwearing and cheap.
The tools you need are a couple of scaffold planks, a decent rake, a wheelbarrow, and an old breadknife for cutting the turf.
When your turf is delivered, we're talking a few pallets here, you'll need to cover it to make sure it doesn't dry out.
Roll out your first turve on the edge of your space. Next roll out another next to the first as close as you can, almost but not quite overlapping. Cut about 2 feet off the end of the turve. Place your board on the join and walk along it to close the join,( avoid walking on new turf for at least 3 weeks). Then roll out the third but don't cut off the end. Again tamp down the seam.
What you are aiming for is a sort of brickwork pattern with as few seams as possible in an area.
Rules to remember; always use a full width of turf at the edges of the lawn, if you use fiddly bits they will dry out. Any off cuts can be worked into the pattern to maintain the staggered effect.
Lastly ,water copiously every night.it will dry up at an alarming rate if you don't.
Good luck.