Payment Plan is a PRO feature.
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
Screenshot:

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
Screenshot:

You can set the percentage of the amount according to your need.
You can buy the PRO plugin from this URL: Advanced – Deposit & Partial Payments for WooCommerce PRO