For this, so far I factored it and did the long division thing and got 2x^2 - 2
How would I go about doing b)? how do i know what to sub in, etc.
Even though this is a correct (though not complete) factorisation, you didn't follow the instructions you were given. You are expected to know that if f(a) = 0, then (x - a) is a factor. So being told that f(1) = 0, you should know that (x - 1) is a factor and that you are supposed to divide by (x - 1).
Assuming you have done that or if you want to continue with what you have done, now factorise the quadratic factor.