Sign-in to the Okta Tenant and go to the admin interface. If you see the Okta Dashboard after sign-in, click on the Admin button in the top right corner.
Go to Directory -> Groups and click on Add group.
Enter AWS PowerUserAccess and click on Save. Optionally provide the group description Enables PowerUserAccess to an AWS Account.
Click again on Add Group, enter AWS ViewOnlyAccess and click on Save. Optionally provide the group description Enables ViewOnlyAccess to an AWS Account.