You have shared no information about the layout of the premises.
Broadly speaking, if you moved into the premises on an annual lease and have been allowed to use the garage without objection for much of the year, and the landlord omits any mention of the garage, the landlord is likely in a poor position to argue that the established use of the garage is not contemplated by the lease.
If you're a month-to-month tenant, the landlord can change the arrangement by giving notice at least thirty days before the end of the month. See New York Statutes, RPP, Sec. 232-a. There could be a local ordinance or a term in your lease that affects the notice period.
The rest depends on the more detailed facts.

