I am 17 and this is my first time doing my taxes how do i now my rrsp limit is

You will need to first file your income tax return so that an RRSP deduction limit can be generated for you.  Your RRSP deduction limit is 18% of your earned income, to a maximum value for the year.    Unused contributions are carried forward each year, so if you didn't maximize your RRSPs last year, the unused amounts are added to this year's limit.