Setting file / folder permissions in Windows

First off, add them under full control before doing this.

1) Right Click Folder
2) Security Tab
3) Edit
4) Add user name from domain or system
5) Select Full Control
6) OK

Remember that even if the users are added in full control, the added user may not be able to add new files or edit existing files in the folder. You need to add the user as a co-owner.

The way to do this,

1) Right click the folder.
2) Under Sharing Tab press share.
3) Share it with specific users you want and change the permission of the user as 'Co-owner;.

This will allow the user to edit files in the folder and even add or delete.

Hope this helps!