If you are a site collection administrator for a site, a link for the second-stage recycle bin will show up on the Recycle Bin page, as shown in the following screenshot:
You can also access the second-stage Recycle Bin by appending the value ?View=2 to the end of the SharePoint site URL; for example, https://<tenant>.sharepoint.com/sites/<site>/_layouts/15/AdminRecycleBin.aspx?View=2.
Once you are in the second-stage Recycle Bin, you can select a few files and click either Restore Selection or Delete Selection:
The ...
