@KGB
I’ve just pasted it below for you 
To share a post, go into the post you want to share and it’s best to go up to the top of it and click on the three dots next to Reply.
From there you click on the chain link I’ve highlighted in red…
…and you get something like this.
Click on the highlighted doc image and you get a green tick beside the url.
Then click the x to close, go to the post where you want to put the link and insert/paste.
I’m on a computer so I don’t know if it’s slightly different for phone or tablets