Source:http://www.hawkdive.com/2015/12/EnableOwnershipOnTimeMachineBackupDisk.html

Method 1. Enable Ownership from Finder

1. Select the drive you want to turn the Ownership on.
2. Press Command+I (or choose File > Get Info).
Enable Ownership on Time Machine Backup Disk
Enable Ownership on Time Machine Backup Disk
3. Twirl open the Sharing and Permissions triangle and look toward the bottom.
4. If necessary, click the lock icon , then enter an administrator name and password.
5. Check the box saying “Ignore ownership on this volume”


Method 2. Enable Ownership from Finder

1. Open Terminal.
2. Type the command diskutil list to know the disk identifier.

$ diskutil list
/dev/disk2
#: TYPE NAME SIZE IDENTIFIER
0: Disk Image *41.0 MB disk2

3. Then type the command "sudo diskutil enableOwnership diskidentifier" and then type the administrator password when prompted.

$ sudo diskutil enableOwnership disk2
File system user/group ownership enabled

For detailed information on tis topics read post http://www.hawkdive.com/2015/12/EnableOwnershipOnTimeMachineBackupDisk.html