Start with deciding how long you'd like you top/cover-up to be. You need twice the length in fabric measured from your shoulders. Cut the fabric at it's desired length (keeping in mind that you mind want some extra to make a nice border). Finish the edges (so that is the bottom of your top/cover-up).
Fold your fabric once in length, and once in it's width. This is where you will cut the hole for your neck. The hole is nowhere near the edges of the fabric.
From the middle point of the fabric (if you would fold it open again), you need to cut a small split. For me, I cut a hole of 13cm in the width and 2 cm in the length.
After you cut the hole, the unfolded fabric looks like below. Finish the edges.
Fold the fabric again. Just once this time. You will now need to decide where your armholes will be. The opening will start from the shoulder and I gave myself 35 cm from the top. I used the pattern in the fabric to determine where I would place the armholes, but make sure you have at least your circumference at the broadest part (for us females, usually at the bosom). I used chiffon, which does not have any stretch, so I made sure it was more than my circumference (70 cm between the stitches).
Then I started sewing in a straight line down. Here, I only sewed for 14 cm. Since there is enough fabric on both sides, even for the cover-up (ankle length), it falls completely closed, but gives you the freedom to walk unrestricted. I would recommend not to sew below hip length.
That's all, it's ready to wear now!