Presumably, you're trying to graph y = 4arctan(2x) and want to know how the 2x makes the graph different to 4arctanx?
Well, if you are, it condenses the graph, in the horizontal direction, by a factor of 2 (i.e. it is half as dilated from left to right).
Consider the value, x = 1/2
Now, that will do the same thing as x = 1 will do to 4arctanx, and the y value will be pi/4 in both cases. If this applies to all values of x, then you should be able to picture that the graph will condense as stated.
Note that 4arctan(2x) has horizontal asymptotes, y = +-(2pi) and, hence, a range of -2pi < y < 2pi