Go to the Invoice/Account -> Configuration -> "Payment Provider"

Here you can see the M-Pesa option.

Enter the credentials (Customer Key, Consumer Secret, Business Short Code/Paybill, and Passkey) obtained from the M-Pesa portal.
Enable state or test mode as per your preference and publish it.

Click on the "Enable Payment Methods" under the Configuration tab.

Activate the M-Pesa payment method.

Now you can see the M-Pesa payment option available on the website.

An STK push notification will be sent to the partner's registered mobile number.
Once the payment is successful, the order will be confirmed.

You can also see the M-Pesa payment option in the portal.

Here, you can see that the payment has been successfully paid.

To enable payment from the invoice, configure the M-Pesa account.

In the invoice, click the “M-Pesa STK” button.
After that, the Register Payment wizard will appear.
Enter the required details and click on the “Create Payment” button.

In the payment you can see the invoice number (Memo).

In the invoice list view, select the invoices and click on the "M-Pesa Payment Reminder" from the Action.

After that, the M-Pesa Mail wizard will appear.
Enable the “Include M-Pesa Payment Link” boolean and click on the “Send” button.

After that, a payment link will be added to the email. When the customer clicks the link, an M-Pesa STK notification will be sent for the total amount.

If you want payments to be created automatically when a customer pays through M-Pesa using the merchant details provided, you can enable the webhook flow.
This setting determines how to handle cases where a customer makes a payment, but the response fails to reach Odoo.
There are two options available: Confirm Payment or Cancel Payment.