Through the ADEA AADSAS portal, you can send up to 4 letters of recommendation requests. When you apply, there is a section of the application where you enter each evaluators email. ADEA AADSAS will then reach out to each of them directly to retrieve the letter. You should waive your right to view the letter, as indicated in the application. This ensures you didn’t tamper with the letters in any way.
For most schools, aim to have letters from 2 science professors, 1 dentist, and 1 person that can speak highly of you like another professor or job manager.
When asking a professor for a letter of recommendation, I used the following packet: Letter of recommendation packet