Once you have opened the new item record, completed all required fields and hit saved, you submit a record by selecting send to workflow, Submit a New Item and Start.
You will see a green success message at the bottom of the record. Once this message is displayed, your record has been successfully submitted.
If your record is already locked in workflow or the "Send to Workflow" button is not available, follow the instructions here: My New Item is Not Submitted AND Locked in Workflow