Right-click that file/folder and click share.
3. You will get a screen like below. Enter the email address for whom you would like to share with.

4. The pencil icon on the right side has a drop-down menu to control if that person may
read only
or will be able to edit the document. Pick the setting you would like for the person who you are sharing the document with have.
5. Click done and they should receive
and
email shortly.
Remember when you share a folder you share all contents within that folder.