When you shop online, Klarna's system reviews each order to determine which payment options are available to you. If Slice it is offered, simply select this option.
The first time you shop with Slice it you'll be asked to apply for a Klarna account. If you're approved, Klarna will create an account for you and your order will be placed. After that, every time you shop with Slice it you only need to agree to the purchase and won't have to sign up again. The order amount will be added to your Klarna Account as additional promotional plans.