In ADMIN click on PRESENTATION and then THEME EDITOR. The file you need to look at with the DEFAULT template is “Main Index Template”, so click on it (on RHS list)
About 8-10 lines down you can see:
<div class="entry">
<?php the_content('Read the rest of this entry »'); ?>
</div>
If you use the <!--more--> tag in your post, then the message that is shown is "Read the rest of this entry »" with a link.
Want to change the message?
That's easy enough to do - just be CAREFUL to leave the single quote marks at the start and end of your new message when you change it in the line above... and DON'T include APOSTROPHES in the message 
However if you DON'T want to use the <!--more--> tag in your post, then you can do something slightly different...
default wordpress theme excerpt Quicktags themes WordPressIf you like this post, buy me a coffeePopularity: 35% [?]
June 2nd, 2007 at 10:31 am
[...] For example, with the WordPress Classic theme I tried to include the_excerpt tag on the main index page to show summaries of the posts on the home page. [...]