How to manage folder permissions?

Firstly you have 100% control over how you want to share your library: 

1. You can share a library with another user

Step 1: 

In my libraries section, navigate to "more operations" button which is next to share and delete icons:     

Then click on "Folder Permission" 

Step 2. 

You can choose if this library is read-write or just read-only

2. You can share with any group that you belong to. You can also choose to give read-write or just read-only permission. 

Now the next logical question you may have is how do you manage group permissions, read here: How to manage group permissions