Open the process definition within the designer and drag the “setformfieldvalues” step from the toolbox to the designer.  Connect the new step to the last step in the process. 

Click on the step and configure the following values for the properties:

Let’s click on the mappings button and set the first name field to the value of “Joe”.

Save the step properties and process definition and let’s re-execute the process instance. Once the instance executes, open the task and enter a value of “Bill” for the first name.

Note: For form fields 'Label' type, select the 'Globalize' check box to globalize the label values.

Submit the task and navigate to the form Instances page within the configuration manager.  Select the form instance “Simpson” and render the form, you should see the value “Joel” within the first name field.