After you have logged in, you can proceed to the unfinished or next lesson by clicking on the “Continue” button as shown.
Do note that LeMS course hierarchy is course->lessons->topics->quizzes. Hence you are required to go through the topic and pass its quiz first before you can proceed further.
When you finish a lesson/topic/quiz, you will see a strikethrough on the respective headings as depicted below. After you have completed a lesson/topic/quiz, there will a be tick displayed to indicate such completion as shown below.