Once you add a contact you can access different actions by tapping on the […] sign that is next to the contact’s name. Those actions are:
Click on “Add Note” to write down notes and choose tags related to the contact or the presentation to this contact.
You can check the notes related to this contact as well as add new notes about him/her once the presentation has already started as well.
Just click on the contact's name on the left side bar and the menu will pop-up again:
Each time you add a note, it is logged as a separate note under the individual contact record. You can also sort by contacts who have notes in the contact listing to simplify exports.