Brazil nuts are by far the easiest and most efficient way to make sure you meet your selenium needs! For adults, men and women require 70ug and 60ug of selenium daily, respectively. It’s also important to know that the upper limit of selenium intake in a day is 400ug (meaning it may negatively impact your health if you have more than this!).
Reference: https://www.nrv.gov.au/nutrients/selenium
Just ONE Brazil nut contains approximately 60-90ug of selenium, depending on the size! Therefore, eating 1-2 Brazil nuts each day means you will easily be meeting your requirements. Try to get into the habit of eating them daily at the same time (e.g. with breakfast or with your afternoon snack) to ensure you stay consistent! Be careful not to eat more than 1-2 nuts per day though as too much selenium can be harmful (as previously mentioned).
Reference: https://www.foodstandards.gov.au/science/monitoringnutrients/afcd/Pages/foodsearch.aspx