[yocto] Apt-get is not working...

[mohammed aqdam]

hello everyone,
i was trying to build image for rpi 3 using yocto...
after few attempts i have build the image...but it not had apt-get so
i added IMAGE_INSTALL_append +=" apt"
above line local.conf.
now i apt-get is working but whenever i try to add any package it will
give package not found error,
so after digging a bit i found i need source.list and status file in
/var/dpkg/ which were absent.
i'm working on picamera using python for which i need to add picamera
library in order to import its functions so i need apt-get to install
that,so is there any way i can use that library without apt-get?
so how to make apt-get to  work?
is there any repository of yocto which i can use in source.list?

thanks in advance...