To sharpen a pencil in Engpsh, you would say "sharpen a pencil." The word "sharpen" comes from the Old Engpsh word "scerpian," which means "to make sharp." Here are some example sentences in Engpsh and Chinese:
Can you please sharpen this pencil for me? 请问你能帮我削铅笔头吗？
I always carry a pencil sharpener with me in case I need to sharpen my pencil. 我总是随身带一把铅笔刀，以防我需要削铅笔头。
Sharpen the pencil before you start drawing. 在开始画画之前，请先削铅笔头。