Is there a way to add that one item that requires recurring payments to

Is there a way to add that one item that requires recurring payments to our current product form ?

I have cloned your form named "Product Order Form" on my side in order to investigate it. I have seen that you sell products, not subscriptions. In order to receive recurring payments, you need to sell subscriptions, not products as you can see in that guide.

Besides, if you want to select the product by default, you are able to select it on the form as you can see the screenshot below:

I hope this helps. 

Please let us know if you need any further clarification.