If you have been away from your course for a while, you can continue it however works best for you. If you remember a lot of what you learned, you can start from the last lesson you completed.
If you do not remember what you have learned so far, but you took good notes, you can review your notes, start practicing again, and continue from the last lesson you completed.
If you feel you would benefit from reviewing the lessons you have already taken, then you could start at the beginning again.
No matter which way you choose, remember to take notes and schedule time for review as well as method practice, so that you can achieve optimal results!