Before you can set up 2-Step Verification for your Notion account you'll need to download Notion Authenticator App on your device by searching for it in your Apple device's App Store or click on the button below Download on the App Store.

Sign in to your Notion account, click on Settings & members at the top left corner.

Under the My account section click the toggle switch to turn on 2-step verification

Select Code from authenticator

In this step is shown the QR Code that contains the secret key which you need to scan with Authenticator App. Keep the page open as you reach for your device.
Note: Do not scan the DEMO QR Code shown below.

Open Authenticator App, tap the plus button, and hold your device up to the computer screen to scan the QR Code from Notion web page.

After successfully scanning the QR Code given by Notion, Authenticator App will automatically choose the Notion logo and autofill the account name and secret key. Click on Save when ready.
Tip: You can choose the account icon by pressing on icon

Go back to the Notion web page, type in the name of the Authenticator App to help you remember it later. Then, click Continue to proceed.

Type in the one-time code from Authenticator App in the appropriate field to complete the setup. When done click Verify code.

You have successfully enabled two-factor authentication (2FA) to protect your Notion account, from now on, you will need to use the Authenticator App when you would like to log in to your Notion account. You can copy the backup codes into Authenticator App or save them in a safe place. Press I've saved them and that's all.