Here are some examples of how it's used:
* He enlisted in the army after high school.
* The military is encouraging young people to enlist.
* She decided to enlist in the navy.
It's possible you might be thinking of a similar-sounding word, like "enlistment," which is the noun form of "enlist". Enlistment refers to the act of joining the armed forces or the period of time someone serves in the military.
Could you please clarify what you meant by "enilist"?