If you want to get a fresh set of proxies, simply follow these steps:
Go to the Proxy List page.
Click the Replace All button.
If you don't have an on-demand refresh on your plan, you can just add that by clicking the Upgrade button on the window that appeared and completing the checkout.
Once you're back on the Proxy List page, click the Replace All button again.
Finally, click Refresh Now to receive a new proxy list.