Thanks for helping out, Alex! I appreciate it 🙂
Instead of just clicking the download link, right click (or the Mac equivalent) and select “Download Linked File As..”. It may say that, or “Save File As..”, “Save Linked File As..” etc..
When you select that option, it will save a file named gp_premium.zip to your computer.
Then you can go to “Plugins > Add New > Upload” and upload gp_premium.zip.
Let me know if this helps or not 🙂