It presents ‘help’, that tells,‘me’, nothing!
(There are many file types accepted for upload.)
The attachment (upload) tool is iconised with a paperclip shown in the toolbar above the editing range while you enter/edit a question or an answer. However, you need a few “karma” points to be allowed to upload files.
If I remember correctly you stated that yourself some time ago, and asked how to get “karma”. Once again:
You get “karma” awarded if any one of your questions is upvoted or your answer is upvoted/accepted as solution by someone else. Users will tend to upvote a question if it is interesting, clear, well worded…
Not yet being allowed to attach files here you may use one of the general upload sevices and insert the URL to your post here.
Quoting @librebel: “How did you get 75 medals…”
Any user’s page will show you under “Badges” what badges were awarded.