For posting a message, you just have to type your text in the compose box (it should be at the left of your screen on a desktop) and then click on TOOT.
You can adjust the audience of your message by clicking on the third icon below the compose box.
There is four privacy levels on Mastodon:
1. Public: everyone can see your message.
2. Unlisted: everyone can see your message but it won't appear in the public timelines.
3. Followers-only: only your logged-in followers and the mentioned users will be able to see your message.
4. Direct: only the mentioned users will see it.
Privacy levels are one of the most powerful feature of Mastodon.
@amj Oops. I forgot to switch it to English.
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