Create your product as outlined in the "How do I create a subscription product?" instructions. 

When you reach the selection for Product Type, select Combined Subscription from the pulldown menu. 
 

This will open up the additional fields needed to add child subscription products to your combined subscription product.

Populate your License Type, Resource Type, Duration. Then you are ready to add child subscription products. 

Click on the Add Bundle Products to add the child subscription products to your combined subscription product. This will open the products tray to make selections. 

Continue adding products to your combined subscription 

If you want to make the combined subscription product recurring, click on the Add A Custom Field Group button and select Recurring Billing from the pulldown menu. Populate this with your recurring price the customer should pay and the duration of the recurring term.

Make sure to hit Publish (if you want it live) and Save, then Clear Site Cache to be ready to use your new product.