I have followed the steps successfully as described below https://wiki.alpinelinux.org/wiki/How_to_make_a_custom_ISO_image_with_mkimage
I can add a package which will be available for apk add when running the live iso. However, I don't know how to install the package into the iso, so that the software is already installed when running the live iso.
apks="$apks ...
inside themkimg
profile script to make you package available during the live image run?