How to share or create unique permissions for a folder

Instructions

In a document library, select the folder to receive unique permissions. Then use the i or "details" to open the information pane. At the top of the pane will be a link called 'Manage Access'. Select this.

1) Instead of Sharing, use Grant Access.
2) Where prompted, either type the name of an individual or a SharePoint group on your site.
3) Assign the correct permission

You can also remove groups or individuals this way. Under the 'Direct Access' section simply select the drop down arrow next to a group or individual and Stop Sharing.