Get your fabric laid out (right sides together...and if the front and the back look a lot alike, put some tape on the wrong side so you don't get mixed up later when you are working in a dim basement :) For the pattern, either use a skirt you already have as a guide, or just do some math.
For the math version:
Skirt front and back
Measure the spot around your hip/waist where you want the skirt's waistband to sit. Let's use the number 40" since its a nice round number.
Now divide that measurement by 4. 40/4 =10 inches
On the fold of the fabric, measure a line 10" arcross at the top of the skirt
Note: Its stretchy fabric, so I don't leave much of a seam allowance, but you can if you want.
Now find out how many inches long you want the skirt to be, then add an inch for some hemming allowance. (Lets say about 36 inches).
Next, you need to make the measurement for the bottom of the skirt. You can make this as wide as you want. I'd suggest that you make the bottom at least 4" more than the top (our top was 10", so the bottom would need to be at least 14")--but it doesn't matter. If you want a fuller skirt, make it 6 or 8 inches more than the top.
For the back skirt piece. If you have enough fabric length, just do an identical piece to the front along the fold (it depends on how long you need your skirt to be--if you are taller than my 5'7", you might need more than 2 yards of fabric--OR--don't cut it on the fold. Instead, cut it on the leftover space from the front skirt piece. You'll end up with two pieces that need a back seam sewed, but it works.
Now that you have a front piece and a back piece (note, if you had to cut the back in two pieces, please sew the center seam, right sides together)--you need to sew the side seams. If you have a patterned fabric, you can try lining up the pattern, or not. It is a pretty casual skirt.
Once you have the skirt body done, try it on--if its too big, you can always re-sew the side seams a bit closer.
Its time to make the fold-over (yoga style) waistband. Let's take that waist measurement again, 40"-we'll need a rectangle of fabric that is 40"x 15" (the 15 is a flexible number. I like my fold over waistband pretty wide, but you can make it narrower if you like). The 40" need to be the stretchy direction (so theoretically you could stretch that 40" to more than that...if it doesn't stretch, then you're going the wrong direction on the fabric). Note. I like to actually measure the distance between the side seams on the skirt body and use that as my official waistband measurement. It means that for sure the waistband will fit the skirt body precisely.
Fold the rectangle in half (right sides together) so that you end up with a 20x15 piece and sew the side seam, making a tube (You'll note that I didn't have a single piece big enough, so I did 2 20x15 pieces and sewed both edges).
Now fold the tube down so that you have a tube that is 7.5 inches tall and 20 inches (or so) across. The right side of the fabric should be all you see on the tube. (Hmmm, I also used a quick basting stitch on the raw edges on this example, but I quit doing that because it took more time and didn't really make a difference...I'm lazy apparently).
Last, you have to attached the waistband to the skirt. Leave the skirt inside out. Lay the skirt flat on the ground/table with the waist opening pointing away from you. Leave the tube right side out. The folded edge of the tube should be pointing toward you.
Slide the tube over the skirt so that the folded edge of the tube is pointing toward you and all the raw edges of the tube and the skirt body line up. (sorry, no pic). I like to line up my tube's side seam with the left seam of the skirt body. You'll need to pin the waistband all around. Now use a serger, or a zig-zag stitch on a regular machine to sew the waistband onto the skirt.
You may think you did the waistband backwards, except remember you will be folding the waistband down, hiding that seam :)
Hemming. Knit doesn't fray or ravel...so you could just leave it with no hem. Or just serge it. Or fold it over a couple times and sew a straight stitch around. Up to you.