The main part of the content calendar is an overview of all of your posts. Both published/planned posts as and drafts. Publications you post via the channel itself won't show up in the content calendar. You have to assign the post to a project first.
To publish a post from within the content calendar you have to click on a day in the content calendar. Next, a popup will open. In this popup, you have to choose a project and then the message composer will open.
At the top of each post, you can see at what time the post was or will be published. You can also see the status of the post (published, draft, error etc.) at the top of the post. Drafts will have a gray circle in the top left corner, published a green one, scheduled an orange one and posts that received an error a red one. The color of the background is based on the color you chose for the project.
Hovering over a post in the content calendar reveals a few pictograms. Published posts and posts with an error have to options. The notepad, which is the 'publication log' button and the two bent arrows, which is the 'republish' button. In the publication log, you can see who created and/or edited the post, to which channel the post was published or was tried to be published, and in the case of an error, you see the error here as well. This article explains different publication errors.
With the 'republish' button the post will be copied into a draft. This can help you plan similar posts way faster! Drafts and scheduled posts show two extra buttons. The sheet of paper which is the 'edit' button and the trash bin which is the 'delete' button.
In the top left corner of the calendar, you can see three different options. The 'Today' button sends you back to the current day and thus week. Next to this button you can see the week you're currently in and you can also switch weeks with the arrows on both sides. The last one is a 'Refresh' button for if you want to be sure the calendar is up to date.
In the top right corner, you see a small calendar. This small calendar helps you navigate to other dates.