open terminal, type gedit /etc/apt/sources.listadd following codes: deb http://http.kali.org/kali kali-rolling main non-free
open terminal, type :
gedit /etc/apt/sources.listadd following codes:
deb http://http.kali.org/kali kali-rolling main non-free contrib
deb-src http://http.kali.org/kali kali-rolling main non-free contrib