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.
http://community.wd.com/t/repository-with-software-worked-on-v4-firmware/94532/24
Also see the following threads/posts that mention WordPress:
http://community.wd.com/t/app-webhosting-for-firmware-v4-10-2015/94892
http://community.wd.com/t/hosting-a-website-on-wd-my-cloud/94766/5
http://community.wd.com/t/clean-os-debian-openmediavault-and-other-firmwares/93714/801
http://community.wd.com/t/is-it-possibe-to-have-a-small-web-server-on-my-cloud/146741/3
http://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.
