Reddit only shows up once it can be connected. If you see a Reddit tile on your profile card in Profiles, you can connect an account and post there.
How a Reddit post works
Reddit doesn't get the video file. It gets your title and a link to a public watch page for the video. The watch page plays the video with your title and caption under it. Search engines don't list it.
Post to Reddit
Start posting as usual, and select one Reddit account on the Where? step. A post can go to only one Reddit account.
On the Text step, write a title. Reddit needs one, up to 300 characters. Your caption shows on the watch page.
In the Reddit section, type one Subreddit name, like videos. It has 3 to 21 letters, numbers or underscores.
Add a Flair (optional) if the subreddit requires one, up to 64 characters.
Switch on NSFW or Spoiler if they apply.
Continue, then send the post.
Check the subreddit's rules on link posts before you post. Reddit has no first comments.
Turn the watch page off or on
After you post, the video's page shows a Watch page line under the post.
Tap Open to view it, or Copy to copy its link.
Tap Turn off to stop anyone from watching it. The link then says the video isn't available.
Tap Turn on to bring it back.
You can't turn the page off while the Reddit post hasn't gone out yet, because Reddit would link to a dead page. Cancel the post instead. Cancelling a Reddit post also turns its watch page off. To retry a failed Reddit post, turn the watch page back on first.