As Felix says you should go through the tutorial, or you could use the staytime histogram.
For the collector, in short, you will need to match the multiple events to one record/row in the stats collector in order to create the entry when the item arrives and update it when it leaves. The best way to do this is to identify the row using the 'item' data label created by the events - this is done by entering 'data.item' into the "Row value(s)" field for each event. Think of that as the "row identifier". Then you can use the time options in the "columns" tab for each field (column) to record the time of the event. Lastly you need to say on that tab which event updates which fields (the lower section).
Also, you're not going to get a histogram with time stamp entries - you need a time duration (typically a staytime, which is why I mentioned that to begin with).
