Pay with a mada, Visa or Mastercard card, credit or debit, or split the cost with Tamara. According to the page, card payments are pre-authorised when you order and charged for real after delivery, yet the same answer says Tamara and Visa payments are collected the moment checkout finishes, so expect the money may leave your account straight away. You cannot switch payment method after paying; the order has to be cancelled and placed again.
With Tamara you can spread the cost over 4, 3 or 2 payments, interest-free and without hidden charges, or settle the full amount and receive special perks from Tamara. Purchases below SAR 2,500 can be spread over up to 4 months, while larger ones can stretch to 12 months subject to your credit limit; the plans you end up seeing depend on how much the order is and your history with Tamara. Tamara operates in line with Islamic Sharia.
Source: LG Saudi Arabia: FAQ (payment and Tamara)