I have my blog pages set up as 3-column, but the page is showing the full stories rather than an excerpt and ‘read more’ function (like shown in the demo). How can I adjust these settings?
To start showing excerpts instead of full posts you need to insert the ‘more tag’ into each of the posts (just like in the demo content). This is native WP functionality. Here is how to use the ‘more tag’: https://en.support.wordpress.com/more-tag.