can't add my present account to folder > Get Info > Sharing & Permissions on Macbook Pro
Solution:
Mac > Sys Prefs > Sharing > File Sharing > Shared Folders: select 
Users > Everyone:  changed from 'read' to 'Read &amp; Write' fixes it.

BUT, the best solution is this:
Leave 'Everyone' as 'Read only' or remove 'Everyone'.

Press [+] box and add Mac account that is same name as my current Windows account, and set it to read &amp; write.
What magic!