Follow these steps to give an IAM user admin access(full access):
Go to AWS management console and under Security, Identity & Compliance select IAM
Creating Policies for New User: Move to policies section under IAM and select “AdministratorAccess” (By attaching this policy the user gets all the Admin access to all the services)
And Vola! You've given a user full access. If you wish to give limited access, then search for the privilege access you wish to five and attach only those.