Payment Plan is a PRO feature.
At first, We have to create payment plans. Go Partial Payment-> Payment Plan.
For example, The product price is $100.
Now we want to create 3 months installment payment plan. So, customers will pay:
- 10% as a down payment/initial payment
- 30% after 1 month
- 30% after 2 months
- 30% after 3 months

Now we will create 6 months installment payment plan. So, customers will pay:
- 10% as a down payment/initial payment
- 15% after 1 month
- 15% after 2 months
- 15% after 3 months
- 15% after 4 months
- 15% after 5 months
- 15% after 6 months

You can set the percentage of the amount according to your need.
To assign payment plans with the product, go to Products-> Add New or edit the existing product page. And click the Deposit tab.

Exclude this product: Click on the checkbox if you want to apply a different deposit type to a single product. By default, it comes from global settings.
Enable Deposit: Click on the checkbox if you want to enable this feature for this product.
Deposit type: Select Payment Plan from the dropdown list.
Payment plan(s): Click here to select the payment plan(s).
And click on the publish/update button. That’s all.
Output:

You can buy the PRO plugin from this URL: Advanced – Deposit & Partial Payments for WooCommerce PRO