Once step 1 is done you will receive a GitHub Invite to the email account associated with your PUBLIC GitHub Account that you associated with your rdkcentral account, make sure you click on the invite.
if you haven't received the invite within 24 hours then please send a support request to support@rdkcentral.com
check https://github.com/settings/emails to see what your public GitHub primary email and other accounts are configured as for the public account you are using
make sure to check Junk/Spam/Filtered emails if you don't see it