If you haven’t already done so you should read through the My Cloud User Manual (http://support.wdc.com/product.aspx?ID=904) which explains how to use the various features/options of the My Cloud network attached storage device.
Officially you cannot reformat the single bay/single hard drive My Cloud units into some other format. You simply plug them into the network (Gigabit router if you have one) and assign it a unique name if you plan on using more than one My Cloud device on the local network. You access the My Cloud Dashboard to configure the My Cloud name and other features/options.
http://support.wdc.com/KnowledgeBase/answer.aspx?ID=13965
You can map the My Cloud drive/Shares for easier access with Windows File Explorer and Mac Finder.
http://support.wdc.com/knowledgebase/answer.aspx?ID=2676
http://support.wdc.com/knowledgebase/answer.aspx?ID=2686
See the following discussion that covers some basics on copying speed to/from the My Cloud.
If you plan on streaming media to local devices, see the following discussion that explains how to get the most use out of the Twonky DLNA media server embedded within the My Cloud.
https://community.wd.com/t/faq-twonky-dlna-media-server-setup-use/95373
