You can split your post to add a “Continue reading” link on the post index page.
To do so, use the WordPress more tag.
You can find the “More Tag” button in the first row of the editor.
You can further customize the message that displays in the link to the full post content.
You will need to do this in the text view of your editor. Once you have changed to the text editor mode, look for this code:
To customize the message, simply add a space after
and turn it into something like this:
<!--more But wait, there is more-->