Using the forum search feature here are just a few past discussions on installing a torrenting client to a v4.x firmware first gen My Cloud. Note: Installing torrenting clients on the single bay v3.x/v4.x My Cloud units will most likely void the device’s warranty and may cause instability or if done improperly brick (render unusable) the device.
http://community.wd.com/t/clean-os-debian-openmediavault-and-other-firmwares/93714/38
http://community.wd.com/t/app-transmission-various-versions-for-firmware-v4-03-2016/93424
http://community.wd.com/t/guide-transmission-2-82/90903
http://community.wd.com/t/rss-auto-downloading-with-transmission-without-flexget-tested-on-v4/95000
http://community.wd.com/t/guide-installing-qbittorrent-on-wd-my-cloud-for-n00bs/93284/3