It depends on your scenario's size.
If you want to upload it to the forum, do the following:
Below the box in which you type your message, there are some icons, some options, and then there's a field called
Attach file with a fillout line, and a button called
Browse.... Just click this button and browse your computer like you do it with any windows option, until you find the file you want to upload, click on it, and there you have it!
Unfortunately, file size is restricted to 500000 bytes, so if the file you want to upload it larger than that, you must either slice it down and upload it in sepperate files, or place an external link.
*hopefully my explanation is understandable*