There are two ways that students can get new Quests.
Students can volunteer for Quests - Once signed in, students can click the Discover option and select Quests. This will list all Quests that are voluntary and that they qualify for based on the Quest's requirements. This is a great way to use Quest because it doesn't require and any teacher involvement!
Teachers can send Quests to students - Much like sending a coin, teachers click Send, then Quest, then chooses the Quest from the list of available Quests, then chooses the students to receive the Quest.