Firstly you most have at least educational degree up to Bachelors(Bsc), in any maritime institution. You may ask why you need this if you already technical knowledge on electrical, marine engine navigation , management , etc. This standard has been set up by the International maritime organization(IMO) to make sure that all seafarers are been trained in a high standard ways, which help the ship owners to run and maintain there ships in a safety and lost free environment. Shipping been the world largest and most important way of transporting Cargo from one port to the other, should be protected by training a very qualify personnel's, who are capable of managing the ship offshore.
Now, while in your educational time, you are expected to attend to a practical training (Cadet), where the already professionals will teach you practically on the field of your studies (Engine or Deck).
Duties & Responsibility of a Cadet or Trainee :
1) Following the senior offers instructions (very important)
2) You most apply safe working practices in all your duties (All you most have in mind is safety first)
3) To execute assigned duties safely , work procedure, to best ability, and report any hazardous condition with delay to duty officer.
4) Most diligently follow instructions and structure of onboard training , make sure to complete the task or questions listed on the training/cadet record book. Also make sure you keep up to date of your training record book, ask questions on what you dont understand to your duty officer.
5) You most be actively seek to learn the duties of the ranks(mostly the next rank of yours) .