Dip the rhizome in warm water and then place in a large zip bag with some damp soil and place somewhere warm for a week - hot water cupboards are good if you have one. You should see where the buds and roots are and place that accordingly. Worst case scenario the growth will find the light by growing round!

There is no up or down in terms of the ends, these are planted horizontally. Inspect it closely, you should be able to see tiny little bumps along the surface - they should be reddish in colour, but they aren't always, depends how old and dry the rhizome is. These are the 'buds' or eyes which will produce growth, so you place the rhizome horizontally in the pot with those buds facing upwards, and just cover it so that its just below the surface of the soil. Best compost to use for these is John Innes No. 2. If the rhizome isn't displaying anything vaguely red, it can be difficult to tell whether the bumps are incipient root points or growth buds.

Too bad you didn't include a photo. The new buds are usually very close to the old stalk and there are usually a few dried roots sticking out.