The polar form of A+Bi is 



The complex number A+Bi is a vector (arrow) drawn from the point (0,0) to
the point (A,B).

So
The complex number -1-1i is a vector (arrow) drawn from the point (0,0) to
the point (-1,-1), which is this:



We draw the right triangle which has one leg on the x-axis and the other leg
(in green) perpendicular to the x-axis and ending at the point (-1,-1):



Then we calculate r, which is the length of the arrow, by the Pythagorean
theorem:



Then we find θ measured counter-clockwise and swung around from the right
side of the x-axis, indicated by the red arc:



Use the unit circle to find θ since it is a special angle.

So 

The polar form for -1-i is 





if your teacher wants the angle in degrees, or



if your teacher wants the angle in radians.

Edwin