You will need the Full Write Workflows permission or be a Workflow Manager on the workflow to perform this action.
Navigate to the workflow you want to add the person to and choose which task where they should be added. Click on the 3-dots menu in the upper right corner of that task, and choose + Add person.
You can also click on the People tab and then + Add Person, shown below in Steps 1 and 2.
For either method you choose, a pop up will appear with the following fields:
Person - search for the person you want to add to the workflow (Step 3 above)
Workflow - identifies the current workflow and 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)
When finished, click on the Add button to add them to the workflow. Check the box for Keep open and add another if you are adding multiple people to the workflow.
Note: When viewing the People tab, you may notice the person was added with a status of Queued. This means the workflow engine has not moved them into the task yet, but will in the next second or two. You can refresh the table in a couple of seconds to see the row updated to the correct task.
Restrictions
There are some scenarios in which adding a person to a workflow will not be allowed.
The person cannot currently be going through the workflow, i.e., has any status besides Done.
If the person currently has a Done status, the Reentry Buffer must have expired for that person before they can be added again (see below). Note: the Reentry Buffer does not apply to form submissions.
Of course, if they have never gone through the workflow, they will always be added.
Helpful Tips
People can also be added to workflows automatically by setting a trigger on the workflow.
You can also set a person to be automatically added to a workflow based on custom form submissions. This can be based on either the submission itself or based on answers to specific questions.
A person can also be added when they text in to an SMS keyword.