If you are talking about trying to install WordPress to a single bay My Cloud, it is not officially supported (at least under v4.x firmware versions).
You may want to see the following post in the Repository with software worked on v4 firmware thread in the My Cloud subforum.
https://community.wd.com/t/repository-with-software-worked-on-v4-firmware/94532/24
Also see the following threads/posts that mention WordPress:
https://community.wd.com/t/app-webhosting-for-firmware-v4-10-2015/94892
https://community.wd.com/t/hosting-a-website-on-wd-my-cloud/94766/5
https://community.wd.com/t/clean-os-debian-openmediavault-and-other-firmwares/93714/801
https://community.wd.com/t/is-it-possibe-to-have-a-small-web-server-on-my-cloud/146741/3
https://community.wd.com/t/use-http-instead-of-ftp/145100/25
Do a search within the WD My Cloud subforum for “wordpress” for additional threads.
