Payments towards your instalment plan are optional. So, your account won't fall overdue if you choose to only pay your minimum payment. However, your instalment plan will be cancelled and the balance will move onto Flexible Credit, with interest still charged at your standard purchase rate. You'll need to pay the minimum monthly payment, and more when you can afford it.
If you've set up a Direct Debit, it'll automatically be adjusted so Argos Pay collect any monthly instalment payments.