Dishwashers can do most of the cleaning for you, but full sterilization is important after your baby has come in contact with anyone recovering from illness, especially other children who may use their pacifiers or binkies. Thorough cleaning in these cases can help prevent the spread of contagious illnesses like Covid-19.
Beyond that, use your best judgment. Some sources recommend monthly sterilizing, but assuming your water source is safe, the need is generally quite low. As a parent, you can decide your own comfort level when it comes to habits of cleaning and hygiene.
When it is time to sterilize, the process is simple: leave the bottles (including nipples) and pacifiers in a pot of boiling water for five minutes. You can also buy specially designed bottle sterilizers that use steam to kill germs and bacteria.