The above MUO article shows how you use it. Having done this, now visit the Opera add-ons store, and install That permits using Opera-specific add-ons & extensions. If you run Chrome, you first need to install another extension, called CrossPilot this allows installing Opera add-ons into Google Chrome. If you run Opera, you can download it direct. This extension is in fact an item from the Opera add-ons store.
Now, I'd always been led to believe this was impossible in Chrome, given that Google also own YouTube and would much rather you watched YT vids in Chrome than anywhere else. Having a browse through earlier on today:.