If you'd like to send a resource to a specific group within the class, you must use the Students filter on the top bar, explained here : How to: Filter students in the grade book
Here is a short animation
You can add resources from this very same screen with a tap on the small paper clip icon.
Send an e-mail with a single resourceYou can also send resources by e-mail from any other view in iDoceo
The following image shows how to access cell resources and send them by email, selecting Three points > Export > Mail