If you’d like to activate Two-Factor Authentication via SMS, you have to open your "Security" settings in the dropdown menu of your profile’s icon in the top right corner of the main toolbar.
In the "Security" section, please find the paragraph "Two-factor authentication system" and click on the button "Verify Phone" to unlock 2FA via SMS.
Once you click on "Verify Phone", you will be transferred to the "General" settings where you have to enter your phone number and click on "Confirm". You will receive a verification text on your phone, that you should enter within 5 minutes.
When you successfully verify your phone, you have to go back to "Security" settings and activate
2FA via SMS. You will receive another text message that contains a verification code, that should be entered into the corresponding field.
After the activation, you will receive an email confirming your action.