To add tasks to your task list, just click on the check icon in the bottom left corner of Rentlio. A list of tasks/notes will pop out with the option to add a new task.
In order to add your task, click on Add new task and write your note. When you're done, you can save the task by clicking on Add or set a reminder date.
When a task is done, you can mark it as done by simply clicking the white circle next to your note.