Please make sure that the admin has already created their Apple Id. 

Following steps are to be followed to Sign In:

1. Clicking on the link provided below admin will be redirected to ‘Sign In With Apple’ homepage as shown in figure 1.1. https://developer.apple.com/sign-in-with-apple/Fig. 1.1: ‘Sign In With Apple’ Homepage
2. An ‘Account’ button is provided on the top-right corner clicking on which admin will be redirected to the sign in form as shown in figure 1.2.Fig. 1.2: Sign In Form
3. Admin must enter their valid Apple Id and click on . The input field to enter password will appear.
4. Admin must enter their valid ‘Password’ and click on . If the admin has two-factor authentication enabled then they will have to confirm this login from another device.
5. Once signed in to Apple Developer portal, two options are displayed as shown in figure 1.3.Fig. 1.3: Login Homepage
   Admin must click on ‘Certificates, Identifiers & Profiles’ to proceed further.