Here is how to upload a .swf (Flash) file to a WordPress blog using a generic bit of embed code (provided here) and modifying it for your project.
When you publish your Flash project it will generate several files including a .swf (pronounced ‘swif’) file. That’s the important one for our purpose. We’ll come back to it in a minute but first copy the sample embed code below and then create a new post (or page) in WordPress:
<object width="550" height="400">
<param name="movie" value="somefilename.swf">
<embed src="somefilename.swf" width="550" height="400">
With the HTML tab selected in the post (or page) paste the code into your page (or post).
Next, upload the .swf file as you would any other media file (image, audio, etc). Click on the media icon illustrated below and follow the instructions.
When WordPress has finished crunching the file you will see the window below. Copy the URL from the File URL field (highlighted in yellow). If the URL is very long, be sure and copy the entire URL and not just the portion visible in the field.
Go back to the post (or page) and paste the file URL into the embed code so you replace the two parts that read somefilename.swf. You need to do this exactly. The URL should go between the quotation marks, begin with http, show the path to the file, its name and end with .swf.
You may want or need to change the size at which the Flash project will display to make it larger or smaller depending on the space available in your theme. Be careful to change the width and height proportionally (or at least close to it). Also note that sometimes Flash projects don’t display or function properly if changed too much.
If you return to the visual tab you will see the yellow .swf placeholder. Preview the project to be sure it works. You can now write or add media to the post as you see fit.
NOTE: If all else fails you can paste the file URL directly into the post and it will display a link that will open the .swf and play the movie on another page.