First, open the attachments screen from the day view or from inside a lesson
Add an attachment
1) Tap on the '+' button at the bottom right
2) Choose a file or take a picture from one of the options presented. This may look different depending on your phone and the apps you have installed.
Remove an attachment
1) Tap the "edit" button in the toolbar
2) Tap the trash can icon next to the attachment you want to delete
3) Tap "done" in the toolbar when you are finished