Hello Augustine Damola Adeyemi,
Thank you for posting your query in the Microsoft Q&A Community.
I understand that you are currently facing issues creating a new user in your tenant.
Based on your description, you currently do not have permission to create the user. The role needs to be activated before you can perform this operation. Once you activate your Eligible role, it will show under the current role assignments tab.
Follow this link below to get more information on how to activate your Eligible role.
Let me know if further assistance is needed.
Babafemi