You can easily lock objects in Prezi Present. 

When editing your presentations, you're always on the move — dragging and dropping objects in place. To make things easier, you can lock specific content. This way, you can control which objects stay put and which ones you can still move around.

You can choose to lock an individual object or a group of objects. Locked objects cannot be deleted or edited.

1. Select one item or a group of objects by dragging the mouse pointer over them.
2. Right-click and select Lock.
3. To unlock, right-click on the object and select Unlock.