How to provision a new AD account to a user using Roles

We are new to One Identity and trying to provision a new AD account by assigning a business role. Below is our approach:

1. Created a business role hierarchy as below:

           Business Role1 ----- Role Assignment (Account Definitions, Active Directory Groups, Employees, Resources)

                  SubRole1 --- Provide Account Definition for AD

                        SubRole2 ---- Provide access to AD group

2. Assigned the business role to the user

3. Account Definition got assigned to user

The account is not being provisioned in the AD. We can see the user under "Employees without user accounts". Don't know what to do here and how to configure One Identity to provision and create account in Active Directory.

Regards

Gurvinder Singh