1) Of course, you need some baking/greaseproof paper and your baking tin.
2) Cut out a squarish/rectangular piece of baking/greaseproof paper larger than the baking tin.
3) Fold the paper in half, with the opposite edges meeting each other. (The inside of the paper is where you'll be placing your unbaked goodies)
4) Fold the folded piece in half again, into quarters.
5) Fold along the pink line as shown below, making sure the folded edge meet with the other folded edge. (the paper will be divided into eighths)
6) Fold along the pink line so that side (A) meets up with side (B). (The paper will be divided into 16ths)
8) Overturn your baking tin, and place the pointed tip of the folded paper at roughly the centre of the tin.
11) Open up the piece of paper, and voila! You'll get a piece of round shaped paper ready to be put into the baking tin.