How to Create Groups, Tenant Administrators, and Adding Endpoints to the Groups?

Global Admin User does not have the rights to add Endpoints.

The global account controls all the tenants in a single Intel® EMA server installation instance.  A global account is created while doing the EMA software installation. 

The global accounts create the Tenants.

The Tenants:
A tenant is a usage space within the Intel® EMA server which represents a business entity.  For example, a tenant can be a company, or it can be an organization or office location within a company. One Intel® EMA server can support multiple tenants.  The users, endpoint groups, and endpoints under a tenant are separate from those under another tenant.
For reference, view section 1.2 Key Concepts of the Intel® Endpoint Management Assistant (Intel® EMA) Administration and Usage Guide version: 1.10.0