I think you mean the links you post when trying to solve a request?
If so the download link itself is enough.
You can upload to any filehost as long as free download is available.
If you find the link on the net and it's premium only you can also post the link, but remember to tell that it's a premium link. Another user might be able to transfer the link to a free host.
If the link you find is on a host you subscribe to, you don't see the "premium only" message.
You can't post on main site unless you are accepted as uploader.
Some of the links posted are supplied from users who are uploaders on main site. They usually post a link to their own posts.
Other users search main site and if they find the item requested on main they also post the link to the original post.
Links to the original post is only permitted if they are from SAnet or the original releaser. It is not permitted to post links to sites similar to SAnet.