There are two methods of doing this, one where the route is added to the part (shown here), and the other where the part is added to the route
Navigate to Data⇒Production⇒Part
Double click on the part number that is to have the route added, select the Route tab and click New
Enter the route number to be added, or click the search button and double click on the required route from the pop-up window
Enter (or if necessary, amend) the material spec and the production lead time for this part/route combination and then click Save followed by Clear
The route now appears in the list of routes associated with this part number
Click Save