While creating your program registration, click the "Registration Fees" tab at the top of your page. To add a new fee, click "+ New Payment Plan."
Here, you can create custom fees, give the fee a name and description, specific gender and age ranges, an initial fee (full registration fee if not a payment plan), a registration max under Total Available (you can set a max number of registrants for a particular fee), and can select the payment options for the fee and make the fee active.
If you want to create a payment plan, after you fill out the above info and create an initial fee, you click "New Scheduled Payment" to setup the fee schedule. The payment plans are fully customizable and allow you to collect any amount on any date. Click "Save" once all the info has been entered.
After you have saved the fee you can click "Copy Plan" to copy this exact fee, "Edit" to view/edit the payment schedule, or the trash can symbol to delete this fee. While viewing your list of payment plans, hovering your mouse over "Monthly Fee Total" will show a quick view of the payment plans for this fee.