Event place and title
Start by adding the event or organisation where the lecture was given. Search for the name of the event or organisation before you add a new one.
Next, fill in the title of the lecture, talk etc. I the description field you can provide details about the content of the lecture or in which context it was given.
You add persons who have had some kind of role during the lecture, including yourself, under "Persons". Then you add an internal person the activity, the activity shows up on that person's personal AU homepage. Therefore, it is a good idea only to do this if it is agreed. Other users may have created the activity already without adding your name.