You need to enter your billing information and make your first payment, also known as a “binder payment” in order for your plan to be approved! The sooner that you make that binder payment, the sooner your plan will become approved.
Whether or not you make your payment right away depends on how close you are to the end of open enrollment. Open enrollment in most states ends on December 15th for plans starting 1/1/2020. Your binder payment would have to be made before that date in order for your plan to be active for 2020.
It’s best to make the payment as soon as possible to ensure that you don’t miss that deadline, but you do have some time depending on how close you are to the end of open enrollment!