Writing a post
A caption, optionally a picture or a video, and a different wording per network if you want one.
Social → Posts → New post. Write your caption in the big box. Add a link if you have one. Add pictures or a video with Add under Media, from the same library the rest of your site uses.
The Internal title at the top is only ever seen by you. It is how you find this post in a list next month. Leave it and the first few words of the caption are used.
When one caption will not do
X allows 280 characters and LinkedIn allows three thousand. The same sentence rarely suits both.
Under each network you have chosen there is Give it its own wording. Press it and that network gets its own caption; everything else keeps the main one. Change your mind and press Follow the post to put it back.
As you type, the count under the caption shows every network you have selected and how much room is left in each. A number in red means that network would cut your post short.