If your asking is it possible to see who or how many people have accessed a Share, then officially no it is not possible on the single bay/single drive My Cloud units. Unofficially it might be possible but it may involve using SSH to modify the My Cloud firmware to add that functionality or to replace the My Cloud OS with an OS that allows for that functionality.
Use the forum search feature, magnifying glass icon upper right, as this question on tracking user access has been discussed in the past. Here one past such discussion:
https://community.wd.com/t/tracking-monitoring-use-on-my-cloud/94215
Note that past discussion on this issue may be confined to the fist generation v4.x firmware single bay/single drive My Cloud units.
If you are asking how to check the size of a Share one can do so through the My Cloud Dashboard Share page which will indicate the amount of storage space a Share is using. Or one may be able to use Windows File Explorer or Mac Finder to select all items within a Share and check its properties to determine total file storage size of that Shae.
