i am not sure how to do this problem

It sounds like you are trying simplify (-6y)(8y^{5}). If this is the problem then remember the following steps.

Multiply the coefficients: (-6)(8) = -48

Remember that y = y^{1}

Multiply exponential expressions with the same bases: (y^{1})(y^{5}) = y^{6} (add the exponents)

Answer = -48y^{6}