Setting up Method to use SendGrid requires you to generate an API as well as enable 2FA in your SendGrid account.
Within SendGrid Account
Setup SendGrid Server in Method
Using the information from SendGrid's article "Integrating with the SMTP API," we can set up the email server in Method.
In Method, click your Profile icon in the upper-right and then click Account Settings.
Scroll down until you find Communication. Select it to go to its settings.
Within the Email delivery provider, uncheck the checkbox to Use Method's server to deliver emails for you (recommended).
Fill in the fields as shown:
Click Test and wait for on-screen confirmation.