Showing "Read more" posts instead of full posts in Blogger/Blogspot?

I turned on the "full post" option in my Blogger settings and I can't find it anymore. I tried to find it somewhere on the internet but there are many tutorials with code changing only. But I'm pretty sure there is (or was) an option in Blogger for that. I want to show only beginning of my post with that "Read more..." thing on the bottom and I can't figure out how. Please help me, I'm desperate. :)