Limit Availability to Individuals or Groups

The first part of the Release Conditions panel -- Select members -- lets you identify who has access to the content. The default is All Members (i.e., everyone in the class).

Release Conditions panel, membership section highlighted


If you want to limit access to a particular student or set of students, choose "Specific members or groups." You can then choose one or more students from the individual members section and / or one or more groups.

specific members or groups section of panel


If you only make a membership selection, the item will be immediately available to the members you've selected. 

The second part of the panel lets you set further conditions for limiting the item's availability.