To use this tool, you must be a premium member and will need to:
Unlike Project-GC, this website is not an official Groundspeak API partner, and thus is unable to use the API to fetch cache information on your behalf. Here's a step-by-step guide for how to upload your finds:
Go to https://www.geocaching.com/pocket/. You must be a premium member to access this feature.
There is a special built-in Pocket Query called "My Finds". This query generates a list of all your finds. Click on the "Add to Queue" button.
Wait a few seconds then refresh the page. Click on the "Pocket Queries Ready for Download" tab. Click on "My Finds Pocket Query" to download the Pocket Query you just generated. This will be a ZIP archive containing a .gpx file.
Click on the file upload component at the top of this page. Select the .gpx file from the previous step. Click on the "Upload" button.
Do note that the Pocket Query contains more information beyond just cache coordinates, but it does not contain personal information. All information in the Pocket Query is also available on the Geocaching website.
While I assert that this website does not store any uploaded data, you should still be skeptical. As someone who cares about my own online privacy, I encourage you to as well. Please review the content in the .gpx file, and only use this tool if you are comfortable sharing that data.