The vertical asymptote is an undefined value for x. In this equation, the vertical asymptote is x=4 because division by 0 is undefined.
Now solve for x in terms of y and use the same reasoning to find the horizontal asymptote (an undefined value for y)
Also, if you still don't get it, my answer to this question about asymptotes may help as well: https://web2.0calc.com/questions/please-help_30347