It's on the guide Part 3, Section 1, Step 15:
The same goes with all payloads you put there:
https://github.com/AuroraWright/Luma3DS/wiki/Other-features-and-notes#payload-chainloading
Code:
15. Copy Hourglass9.bin from the Hourglass9 zip to the /luma/payloads/ folder on your SD card and rename Hourglass9.bin to start_Hourglass9.bin
The same goes with all payloads you put there:
https://github.com/AuroraWright/Luma3DS/wiki/Other-features-and-notes#payload-chainloading