How can I add a package to ImageBuilder to create my own OpenWRT firmware?

Question

SSH

Hello Guru. Your help is required. Task: build openwrt firmware for the router, which should contain a package called sshtunnel_4-1_ar71xx.ipk ImageBuilder itself works, everything is ok.
So I found and downloaded the necessary file: https://downloads.openwrt.org/snapshots/trunk/ar71...
Question 1: in which folder should I place it so that ImageBuilder finds it?
Question 2: how to name this package in the list of installed ones, so that ImageBuilder would install it into the firmware?
Thanks in advance for your replies!