I'm new to OpenWrt/FriendlyWrt on the building custom made image.
I apologise whether this is FAQ: in such case please forward me to any link as google didn't help after search for an answer.

I'm using a ZBT WE826 loaded with a custom made (LTEFIX) OpenWrt firmware.
I'm not testing the FriendlyARM Nano R1

There are some packages in the LTEFIX firmware which I would like to see them installed on the FriendlyWRT.

My question is...how can I "transfer" or have these packages installed in the FriendlyWRT image I'm going to build ?

For example IPERF3.
How do I include IPERF3 (and it's GUI under LUCI) within FriendlyWRT image I'm going to build ?
Other packages are MWAN (between WAN and WIFI), WIREGUARD, etc....

I need to build a stock image with these programs and have it loaded on R1 eMMC.