In the last column of the grid, you'll find the actions possible on an instance :
Icon Description :
1. a new tab is added with details and activities
corresponding to the selected instance.
2. the instance will be suspended until you click
on the next icon.
3. the instance previously suspended will be
resumed.
4. the instance will be terminated and its state
will be "exited".
5. the instance will be totally removed from the
history base.
Note that these icons are disabled when the actions are not possible.