To add times to each activity on your itinerary, you first want to go to your trip itinerary.
When you have the places and activities added on the correct days, you can click the pencil icon which edits the information.
Then simply click the Add Time, Price, or Tag Specific People text. From there you can add a time as well as time zone (if necessary).
Once completed, your itinerary will automatically organize the times scheduled in order.