You can create a post and add it to the queue to post on different social media. Adding to the queue means that a post will be scheduled and Simplified will pick a time and date for it or (if you have your publishing time slots set up) it will be put into next available time slot.
To do that:
Open your calendar section from the menu bar on the left.
In the upper right corner, click on the +New Post button.
The creating post box will be displayed.
Create a post by writing the content and adjusting it to each chosen account.
Then, at the bottom right of the creating post box, you will see the yellow publish button with an arrow ˅ button
Now click on the arrow ˅ and select add to queue.
The other way to do that:
Open your calendar section from the menu bar on the left
Hit open connected accounts in the top left hand corner
Select the three dots to the right of the social account you wish to set up a queue for and select Account Settings
Then a box will open and go to timetable in the top menu bar
There you can adjust the time and the dates of your queue, you can also select the frequency of your posts
When your done just hit the yellow Add Schedule button