Wraping windows, doors, soffit and fascia, is a learned skill. But, you might be able to rent the most important tool, a Brake, from a rental center or even Home Depot.
It's all about knowing how to measure and knowing what bend to make first. When using a brake, you must know the restrictions of the tool. As a rule, making a bend less than 3/4" is the hardest.
If you have a flat casing, (1 X 5), This is not a big problem. You need to measure from the window to the flat,(3/4" as a rule), then across the flat and then back in again and then add another 3/4" for a flashing bend.
If you have a 908 casing, you will have to figure an 1 1/4 bend 3/4" angle about an 1" then back in again and add 3/4" for the flashing.
This comes with practice and I would only buy 24" coil stock and cut it to the desired width because you should have less waste.
These are only examples and you need to find out what is right for you.
It's all about the math!
Tools needed would be;
A razor knife
A square that will span 24", or at least 12"
(you may need a countersink tool)
Materials would be;
Rolls of 24" aluminum coil stock
1 1/4" plain shank aluminum trim nails, (the same color as the trim)
Lastly, you need to know where to nail and how to overlap so the water runs over you cuts.
The most important thing that you can do to have a good job is to use quality siding. You won't find this at a big box store.
I would think that you would want to use a brand like Certainteed/ Wolerine or Alcoa/Mastic and don't settle for anything less than .042 thickness.