Background - You need to have appropriate rights/permission to activate this site feature.
Steps
- Before activating Nintex feature/Service: Workflow setting shows only default Workflow in SharePoint designer to create and modify Workflow.
- In site actions -> Site Settings-> In Site Actions, click on Manage site features -> activate following Services (Nintex Workflow 2010, Nintex Workflow 2010 Enterprise Reporting).
- After activation of the feature/Service, you can see Nintex Workflow options in Workflow setting.