The orange bar at the top of the website indicates that you are in the free trial phase.
By clicking either on "Get your paid subscription here" in the orange bar or on your profile and then under settings, you can switch to a paid annual subscription at any time during the 7-day free trial period.
In your settings, go to the BILLING tab and then click on the PURCHASE button.
Then choose your desired payment method (credit card or by invoice), fill out the corresponding information, enter your promo code (if you have one) and then click on the PURCHASE button to complete the conversion.
You can view or change your subscription and payment information at any time in your settings. More information about the payment change can be found at: How can I set or manage my payment method?