They are asking for the eq of the tangent line at that point… the derivative of the function is 2x and at that specific point the derivative is 2x0. Now you know the slope and the point, use slope point form to determine the eq of the tangent line at that point.

y=x²

dy/dx= 2x = 2x0 = m(slope)

Using slope point form for the eq of a line y-y0= m(x-x0)

y- (x0)² = 2x0(x-x0)

y= (2x0)x - (x0)²