Farming :
Farming is done on soil, never bare rock. Build a farm plot on soil or mud. (Mud is left by water being on top of rock) Not on bare rock, unless it has mud on top of it.
If it's inside you'll need the seeds of subterranean crops. (You should have some)
If it's outside you'll need the seeds of outside crops. You can go and gather outside shrubs if you order some dwarves to be herbalists.
when your farm plot is done, set up the seasonal alternance of crops as needed. a farm plot has orders of a single crop, or fallow, each season. Fallow means it grows nothing this season.
then if you have seeds, unoccupied dwarves with the Farming (Fields) labor activated, and access to the farm plot, dwarves will start to plant seeds, and they will grow, and dwarves will harvest the crop.
Try growing plump helmets first.
Wells:
You need to build your well over a hole which has water on it. You need to dig and channel so you make a 2z-deep cistern, then build a well over it. You can only build a well over empty space.
Obviously the well will not work if the pit under it is completely dry. The rope and bucket can go downward many z-levels, though.
Wells are made from mechanisms (made from stone at the mechanics's workshop), blocks (made from stone at the mason), and a rope/chain (made from cloth at clothier or metal at the forge/magma forge).
Move corpses and rocks :
Make stone or refuse stockpiles inside your fort, your dwarves will move them to the stockpiles. You have stockpile menus you can use to allow/disallow certain types of refuse or stones in the stockpile.
Butcher animals :
Build a butcher's workshop, have a dwarf with Butchery available, go to the units screen, then go to the animals/pets screen and you can designate animals for butchery.
Preparing meals :
Make a kitchen (it's in buildings/workshops) and order meals done from there. Careful about cooking farm-grown plants, because cooking does not produce seeds and then you run out of seeds.
Making flour or alcohol or processing plants, however, makes seeds.