These are the basic steps. (I'm really sorry if they're absolutely confusing...just ask if you need help. I'm going to try to take some pictures next time)
1) measure your bust
2) take off about 10cm for the length of the fabric (bust measurement -(minus)- 10cm x 60cm width)
3) pick out an elastic strap that's about 1-2cm wide
4) take your bust measurement and take off 20cm for the length of the elastic
5) sew your piece of fabric together at the width (60cm side) with the right sides facing eachother
6) turn inside out so the right sides are facing outwards
7) fold over the top of your fabric about 3-4cm
8) sew that leaving out about 3cm to insert the elastic
9) stick a safety pin through the end of the elastic
10) pull the elastic through the tunnel by pushing it forwards with the safety pin
note: don't let the elastic rotate! and hold on to the other end so it doesn't get pulled in as well
11) once you pulled the elastic through the tunnel completely sew together the two ends (you can do it by hand but also by machine)
optional: 12) since it's jersey you don't need to seam the bottom, but if you want to you can do it at this stage
and DONE! it's really comfortable for those lazy summer days - beside the fact that I dislike my fabric, I love it! haha that just sounds stupid...
plus you can also use it as a skirt if you want to!