If you want to assign a specific notary to an order, just create your new order and click 'Search Agents'. From there, find the notary you want to assign in the search results, without starting the Automator. If the notary is already favorited in your account, you will see them at the top of the search results. Otherwise, follow the instructions here to find the specific notary, or grouping of notaries, you are looking for.
When you find the notary you are looking for, or one who meets your specific qualifications for this order, click the blue 'Assign' button next to their name. Once they accept the signing, they will be automatically assigned to the order.