Begin with 1 yard each of two kinds of fabric, sew on velcro, and thread to match your pattern. (I used white)
Begin by cutting each yard down to 33x41.5 inches and use the excess to cut four 8x2.5 inch strips, two of each fabric. Set the small strips aside, they will later become the straps to secure the canopy to the carseat. Fold the larger pieces of fabric in half then in half again to align all the corners on top of one another and stack both pieces together so there are a total of eight layers you will cut through. Use a round place as template to round the corners of the pattern.
Line up the fabric pieces with the front of the fabric facing each other and begin pinning them in place along the border. Note: My cutting/measuring was not exact so when I lined up the pieces to pin together I had to trim a few centimeters off of one side to make the pieces match. (I had a similar issue with the straps later!) Now you're ready to sew!
Sew the pieces together, I tried to sew the seam about 1 centimeter from the edge of the fabric, and leave a 4 to 8 inch gap to allow you to turn the fabric right-side-out. I left about 4 inches and it worked perfectly.
Once right-side-out, iron the fabric to make all the edges even and to make sewing easier. Now, back to the sewing machine! Sew a seam around the whole pattern, this time I tried to stay about a 1/2 centimeter from the edge. This will also seal the gap that was originally left. And the hardest part is behind you!
Now move on to the straps. Sew the straps front side together along three of the edges and then turn right-side-out. Iron these as well to press the edges and create a more finished appearance Now to the velcro, measure the length of your strap and sew the velcro on going along the edge.
Finally sew the straps to the canopy. The original tutorial recommended 17 inches from the top of the canopy and 12 inches in from each side. I ended up with 11 inches from each side and about 17.5 inches from the top. (Measuring your carseat would give you a better fit for your particular carseat, since I did not have one to measure I estimated and it worked just fine)
And believe it or not, you're done! Mine was far from perfect, as I am not an avid seamstress, but I was so happy with it! It is now on its way to Idaho!
Update: Here are photos of the canopy in action that my cousin sent me when she received it. It looks a little long in the front so don't worry about sewing a wider seem, there will be fabric to spare!