1) open your sharepoint site and select "Documents" on the top left menu
2) Hover over a folder and click on the 3 dot line -> select "details" from the menu
3) The new details that show up on the right click "Manage access" then click on "Advanced"
4) Click on the "Grant Permission" on the top menu bar to add people/groups you want to give permissions to or select a check box under the "Name" table and then select "Remote User Permissions" to remote access to people/groups.
