Go to the Plans tab and click the PLAN on the top-right corner. You will get a pop up window.
You will get a image as shown in below:
You can enter the details
Plan Name is mandatory.
Select the type whether Quantity or Unlimited.
Choose the price you want to add.
Select the currency. Your Product will be listed in Payment Box once you select the currency form dropdown.
Select Billing Type from dropdown whether Monthly, Quarterly etc. Billing Every section
Also select the No. of billing Cycle . If you enter 2 that means billing cycle is for 2 months.
Click Save. Your plan will be listed in the table. That can also be consider as product.