Go to the Operations menu and select Activities
This will give you a list of all Activities in the system. You can filter each of the columns by entering your filter terms in any of the fields at the top of the columns (in red) and you can sort the columns with the up/down arrows by each column (in blue).
To view an Activity, just click on it.
This will show you the details of the Activity. You can Edit/Close/Complete/Delete the Activity.