By default, other users’ files cannot be accessed, not even by an administrator. To get access to other users’ files, you have to add explicit permissions.

1. In the Finder main menu, select Go > Computer or press Command-Shift-C.
2. Double-click your Mac’s partition (usually named Macintosh HD).
3. Double-click the Users folder.
4. Double-click the user folder you want to access (in the image below, test). All folders you currently don’t have access to are marked with a red icon. Trying to open one of those folders will cause an error dialog to appear.





5. Select the folder you want to access, then in the Finder main menu select File > Get Info or press Command-I.
6. Click on the Lock icon in the lower right corner of the Get Info dialog, then authenticate yourself by using Touch ID or entering your password.
7. Click on the + button in the lower left corner, then select your name in the sheet that appears, and finally click on Select.



8. (Optional) The selected user has read-only access by default. To be able to write to the folder, click on the Read only popup button beside the added username and select Read & Write.



9. Close the Get Info dialog by clicking the red title bar button or pressing Command-W.
10. Repeat steps 5-8 for every other folder you want to access.