You will need to be a workflow manager of the workflow, or have the Full Write Workflows permission, to perform this action. The permission must reach at least one of the workflow's campuses. If you are limited to some campuses, you can add your own household and anyone whose profile you can open.
Go to the workflow you want to add the person to and choose the task they should be added to. Click the three-dot menu in the upper right corner of that task, and choose + Add person.
You can also click the People tab and then + Add Person, shown below in steps 1 and 2.
Either way, a window opens with these fields:
Person - search for the person you want to add to the workflow (step 3 above).
Workflow - the current workflow. It can't be changed here.
Task - the task they should start in. When adding from the workflow editor, this is the task you selected. When adding from the People tab, this is the first task of the workflow (step 4 above).
Click Add to add them to the workflow. Check Keep open and add another if you are adding several people.
Note: On the People tab, the person may show a status of Queued. This means the workflow engine has not moved them into the task yet, but will in a second or two. Refresh the table shortly to see the row updated to the correct task.
Restrictions
Adding a person to a workflow is not allowed when:
The person is currently going through the workflow, meaning they have any status other than Done.
The person has a Done status, but the Reentry Buffer has not expired for them yet (see below). The Reentry Buffer does not apply to form submissions.
If they have never gone through the workflow, they can always be added.
Helpful Tips
People can also be added to workflows automatically by setting a trigger on the workflow. See Trigger Task.
A person can be added to a workflow automatically when they submit a custom form, either on any submission or based on their answers. See How do I add automation to a form?
A person can also be added when they text an SMS keyword.