Tools:
<> Good hammer, 18 ounce or heavier.
<> Flat bar, wide wood chisel or flat head screw driver.
<> A rag, to throw a way afterwards.
<> One tube of caulking for every 10' foot of wall.
<> A piece of alluminum coil, how ever many feet long as the wall.
"if you have two walls 10' long, than one piece of metal 10' long will do both, because you don't need a full width of the metal coil"
<> Handfull of masonery nails, 1 1/4" in size.
Higher a handyman, roofer, sider or metal guy. Or follow these steps.
<> Scrape all existing roof cement/tar off the brick, take care to not damage or bend existing step flashings.
<> Run a light bead of caulking across the top of the step flashings,
half on the flashing, half on the wall,
and smooth it in with above mentioned rag.
<> Cut your metal to the lenght you need,
than cut it to 6 inches in height, less if you need to in order to avoid hitting the window but no less than 4", using your hands, carefully, CAREFULLY put a slight bend at the top of the counter flashing, make sure that bend faces the wall when you install the metal.
<> Place the 'pre-cut' metal against the wall with it starting roughly one inch below the start of the step flashings and ending at the ridge above,
the bottom of the metal should be roughly 1" above the break where the roofing and metal meet,
starting at the bottom end place one fastener into the nearest morder joint and firmly pound the fastener in, and continue placing fasteners no less than every 3 feet all the way up the wall to the end,
than caulk all along the top of the counter flashing, half on wall, half on flashing and smooth in with the rag.
Assuming all fasteners went in ok, your done.
If a fastener bends or breaks the morder, you can repait that with simply caulking the hole really well, but take care not to have many bad fasteners.
Never try and install a fastener any closer than 2" of any corner or extrusion.
Hope I didn't miss anything.
Good Luck.
Edited to add,
you can purchase above mentioned materials and tools at most hardware stores,
especially chains such as Lowes and Home Depot, etc.
But if you go to a local roof supply store and tell the sales rep what your up to,
they can put together a package of what you need, including pre-cutting and bending the metal for efficiency and safety.