Creating a 2013 Nintext Workflow

The 2013 workflows created from the site settings drop down are site level workflows or reusable (added to a content type). You are probably looking for how to create list workflows.

To create a list workflow, go to any list or library, under the library tab in the ribbon to the far right is a button for workflow settings. Hit the drop down there and find Create a Workflow in Nintex Workflow. For instructions with screen shots, review How to Create a Leave Request Workflow

If you are unable to see the link to create nintex workflows from a list/library, then most likely the Nintex features were not activated for that site. See Installing Nintex Workflow 2013 and Nintex Forms 2013 on page 25 it starts a section "Activate features in SharePoint"

Hope this helps, let me know if you are still missing anything or cannot find what you need.

Robert, this is because Nintex in 2013 uses the SharePoint 2010 workflow engine. In SharePoint 2013 there is two workflow engines you can choose from. Details are outlined here. Further down the track we'll add support for the workflow manager engine but at this stage all workflows create with Nintex will show up as SharePoint 2010 workflows.

Hope that clarifies it

To date, workflows created on-premise 2013 within Nintex will not be able to be imported into O365. This could change one day, just not to date unfortunately.