Short Answer:
You can create a post from the Create Post button at the top of the main menu and/or Feed, and from the Quick Actions menu.
Steps:
1. Click create post.
2. Enter a title, add a thumbnail (optional).
3. Add text.
4. Add assets (optional) and click next.
5. Add an Author and choose the date you want the post to go live.
6. Add any relevant search tags.
7. Add the post to any relevant collections you want it to be found in.
8. Decide whether you want the post in your main feed, otherwise it will only be found in the collection you chose.
9. Choose to allow comments or not.
10. Choose the access level to decide what level of member can view the post.