Enable file sharing

1. Start the 'System Preferences' app
2. Click 'General', then click 'Sharing'.
3. Turn on the ‘File Sharing' option.
4. Click the 'i' button to share a folder.

Share a folder

1. Under the 'Shared Folders' lists, click the '+' button.
2. Choose a folder to share and click 'Add' button.
3. By default all users ('Everyone') get read-only access to the share. To give your user the ability to change files, click + under the 'Users' list and choose your account. Then change 'Read Only' to 'Read & Write'. (See the screenshot below)

4. Click the "Options" button, then select “Share files and folders using SMB” and select the user account to authorize access. (See the screenshot below)

About iCloud Password (Apple ID)

If you use your iCloud password(Apple ID) to access your Mac, this account cannot be used to access shares. Becasue it's gray and cannot be selected in sharing settings. See the screenshot below.

To fix this issue, please create a separate password.
1. Open the Users & Groups in System Perferences.
2. Select your account in left panel.
3. Click "Change Password" button.
4. Click "Use Separate Password" button.

Q&A

Q. I get "unknown host" or "timed out" error when accessing the shares. What should I do?
A. There are two things you can have a try.
1. Use the computer IP address to connect, instead of computer name.
2. Restart the file sharing service on your Mac. Turn off the ‘File Sharing’ option and turn it on again to restart the file sharing service.