Note that those instructions are for the; WD MyCloud EX2, WD MyCloud EX4, WD MyCloud EX2100 and WD MyCloud EX4100 (arm based), and on WD MyCloud DL2100 and WD MyCloud DL4100 (Intel based).
This particular forum is for the single drive My Cloud device which is not listed as a supported model at that link. The single drive My Cloud devices do not have the App page like the more expensive models listed above have. However, there is the following My Cloud thread that discusses how to install Bittorrent sync on a WD My Cloud:
https://community.wd.com/t/how-to-install-bittorrent-sync-on-the-wd-my-cloud-windows/91419
