Sharing content in a private group
Sure, you can use the Classroom feature (Groups at the top on the site) to create your group, invite students to join it and share your imported content with your group only.
Thank you Zoran, that's fantastic. Will my students be able to view my content even with a free account?
And it says I've reached the import limit, what is it?
Your account is on a FREE level at the moment, and Free accounts have limited importing available. You have reached limit and can't import more with the Free account.
The classroom feature is available to Free users too, yes.