It's so simple you'll wonder why you had a problem, but difficult to explain without writing a book.  You're typing a post and want a link.  The easiest way is open the place you want go in a second tab then highlight the URL and use Ctrl+c to copy it. Go to your post and highlight the word or words you want to link through.  If you want to use the URL go to where you want it to be, touch Ctrl+v and paste it.  Highlight it and the link button (looks like a log chain).I new bos will open.  Touch Ctrl+v and you'r done