That's last step ! Easiest one . We just need to tether boot second OS with files created in previous step.
First put your device to pwnedDFU and remove signature checks to load unsigned images.
After you put your device to pwnedDFU we need to send our iBSS and iBEC.
irecovery_new -f ibss.img4
irecovery_new -f ibec.img4
Now we need to open irecovery shell using older version of irecovery.
Now we will send and load devicetree.
And to load it we need to just type "devicetree".
After sending devicetree we need to send kernel.
And to boot device we need to type "bootx" and click Enter. Now device should boot to second OS.
Device should boot without problems to second OS if you followed Guide exactly.
You can see that 5 GB that were useless added now to our data partition.