The Fourier Transform and Fraunhofer Diffraction

I’m currently learning about Fraunhofer diffraction and I don’t really understand how it works with the fourier transform and the tophat function. I’m currently struggling on a question involving two thin parallel long slits separated by a distance d illuminated with monochromatic light of wavelength lambda. The question first asked me to derive the Fraunhofer diffraction pattern without using the fourier transform and I got $$Intensity = frac{2U_0^{2}}{r^2}Cos^{2}(frac{kdsintheta}{2})$$

I’m not sure if this is correct, but how would I calculate it using a fourier transform with a delta function with $ x = −d/2 $ and $ x = +d/2 $