In the Vedic Culture, the Rudraksha Mala was gifted to the disciple for starting the life and he took mala as an honor or the remembrance of the Guru. So if a Guru gifts you a mala, never deny just accept it and start wearing. The Shiva day "Monday" is the best day to start wearing the mala. Before wearing the mala, I recommend you to keep this mala in a holy place or burn incense there.
If you are eating meat someday, it is recommended that you keep your mala in your bag and wear it again after the next day's bath. If you have any menstrual period, you can also keep the Rudraksha in the bag and wear it again after your periods.