There is a nice software that i've been using for a while called "Flashpoint Infinity".
Simply search for the name and you should stumble upon their main page where you can download it for free:
At the time of writing, the latest version is 12.1

After downloading, either the installer or the zipped copy (the whole thing but without an installer), you should see a "Start Flashpoint". Double click on that and you will likely see this:
You can click on "Games" on the top left corner, or search for the name right away:
Simply click on the game and a side panel on the right will show up:
For me it says "Play" because i've already download the game, but for you, it will be a big blue rectangle saying "Download". Hit the download buttom!

The reason why i prefer to use Flashpoint Infinity is because the flash game gets downloaded to your machine and that's it! You now have the game's file! You can play completely offline. No need to use a different browser to access a website hosting the game. The games will be saved to:
"Flashpoint 10.1 Infinity\Legacy\htdocs
Ignore the outdated version. I'm simply too lazy to update

After the download is finished (Should be very fast. Flash games are usually pretty small), you're good to go. No need to do anything else other than sit back and enjoy :D
Please spread the word so everyone knows that they can still enjoy flash games.
Thank you for reading!