Clicking "Upgrade" from the Events page will take you to the plan selection page. Pick the preferred plan. Click the "Buy" button. It will take you to the payment page.
This is how the payment page is going to look like. Click "Puy" button to place an order. You will have a confirmation email in your inbox.
If the payment failed, you'll get a "Declined" message shortly.
You can also upgrade your membership from Billing section.
Pick the membership you like and go to payment page.
Note: if you are currently using Proficonf PRO membership, you'll have to click "Change plan" from the "Overview" page. The layout will look something like this:
You will be redirected to the plan selection page.
Click "Downgrade" if you want to switch to the Free plan. To upgrade to Premium, click "Buy".
Note: The payment you will have to make when upgrading from PRO to Premium is the recosting estimate.