It's very simple to put flash elements like games or movies on your site!
The first thing you'll want to do is export your flash movie, of course. In flash, go to File > Export > Export Movie and save it as a swf file. This goes for animations as well- do not save as anything other than a swf.
Let me start by saying that this method will not work if you are using a neocities account that was created after January 2024. It will still work if your site was created before then, or if you have neocities supporter.
You'll want to find a filehost to put your flash movie if you can't upload it directly to your site. I use filegarden for this. Once you have the url of the flash movie, which should end in .swf, take this code and place it where you want the movie to be on your page. Make sure to change the width, height, and url.
Next, you'll notice that you still can't see your movie. That's because you have to add ruffle to your page! Don't worry, it's very easy. You can find the code to do this here. Copy one of the two codes depending on whether you're self hosting ruffle or not, and paste it in the head tag of your html document.
If you've done everything correctly, you should be able to play your movie now, and others visiting the site should too!