
The point of a sewing a hem is to hide the raw edge of the fabric - both to make the garment look more neat and to protect the edge of the fabric from fraying.
This can be machine stitched (as on left) by running a straight line of stitching near the edge that is turned under, or it can be hand stitched (as on right) if you don't want the hemming to show on the right side of the fabric. Use small stitches and try to catch only a thread or a small amount of the fabric with the needle.
In the photo on the left I have tried to show both ways of sewing a hem to help you decide which you would prefer to do. 

rose@ludlowquiltandsew.co.uk
www.ludlowquiltandsew.co.uk