Trying to add " read more" tab but not truncating article

I have the Zimney theme and I am not sure if I am building pages correctly.
I am building the Home Page and am inserting all the code using the buttons provided.
I added some articles to my home page and am trying to use the “read more” tab which places the appropriate line in the code, but when I publish it, it’s not truncating the article or adding the more tab.
Please advise.