The paper should be folded to provide a large amount of surface area (and also to fit better in the funnel). Folding filter paper in the manner described below is a simplified version of the folding procedure (also known as 'fluting' the filter paper).
Fold a piece of large-diameter filter paper in half, then into quarters, and finally into eighths. Unfold the paper and place it fluted into the funnel.
Fold the paper along the dotted lines shown in the diagrams below: