Adding packages to OpenWrt with Image Generator?

Question

linux

Good evening everyone. The question is how to edit the finished OpenWrt firmware and add the packages I need to it using Image Generator. The principle is clear that we write a command like

make image PROFILE=профиль PACKAGES="redsocks" FILES=files/

and accordingly it adds the Redsocks package to our firmware. But it's not like that. An error occurs that such a package was not found, on off. I read on the site that you need to add repositories to the configuration file, that is, add the Ubuntu repository or something, so that it takes this package from there? Or you can add only standard packages to the firmware from the OpenWrt website. I know that you can add any packages when compiling an assembly from scratch, but I would like to bypass just adding to the finished firmware for now. Who will say what?