How to sharpen super dull knife?

I don't mean dull as in it won't cut through this or that but my knife has almost no discernable edge, hell the only way I know which side the edge is on is by sheathing it. My knife is about 4 inches long and made of bronze. Also I can't get a shrpening stone or whetstone as I'm 16 and neither of my parents will help me as they really don't aprove of knives at all.