adverb: using, by means of
verb: to use
The use of kepeken as a verb is... controversial. There are those who insist that kepeken e is improper usage. In my personal opinion, it seems arbitrary to say that this one word can't be used as a verb, even when words like lete and wan can be. Sometimes, kepeken e is the simplest way to express the thing you want to say.
pali kepeken ilo - to work using a tool
kepeken e ilo - to use a tool