Select a file or folder.
Press the sharing icon to view the sharing options.
The following manual shows the steps for sharing a folder. If you want to share a document you have to take the same steps, however for the document only.
Enter the desired user name or mail address. Select the option which is displayed without "(email)" or "(remote)".
The folder is now visible for the other user. Underneath the option sharing you can see which people can see the shared the folder.
You can now adjust the rights accordantly.
To learn more about password protected and expiration date see the different manuals.