If your article is already somewhere on the web then you can post a link to it. The forum won't let you do that until you've made 50 posts (that's to prevent bots spamming the forum) but if you replace the dots with spaces another poster will convert it for you.
If your article is not already on the web, if it's just sitting on your computer, then I'm afraid I don't know how to upload it to the forum; I'm not even sure there is a way of doing that, though another poster might. My suggestion would be to cut & paste your article into this thread, one paragraph per post. You can either wait for comments on each paragraph before posting the next, or post the whole thing in a series of posts and then wait for comments on the whole article. I'd recommend the former, as many posters may be reluctant to read a long screed. It would also enable you to edit later paragraphs in the light of comments on the previous ones before posting them.
It might be a good idea to post a summary of what the article is about first, to get initial feedback and check this is the right audience for it. Be warned: many posters here are well educated in the scientific method and standards of evidence, and some can be impatient with posters who have not educated themselves adequately on these things.
I hope that helps, and welcome to the forum.
ETA: Looking at the 'Manage Attachments' option in the post editor it does look like PDF and other document formats are valid attachments, though I've never seen anyone use them - it's usually used to attach images.
Click on 'Manage Attachments' and then 'Choose File'. Select the file containing the article on your computer, and then click the 'open' button. Click on the Upload button (you may need to widen the width of the popup to see it) and it should upload, though it might tell you the file is too big to upload.
