Hello aellopos,
Follow below steps:
=> Create and active child theme of your current active theme. If you direct change into current active theme it will gone when you update theme so prefer child theme.
=> Add below code into child theme’s functions.php file.
function maxwell_more_link() { ?>
<a href="<?php echo esc_url( get_permalink() ) ?>" class="more-link"><?php esc_html_e( 'Your Text »', 'maxwell' ); ?></a><?php
} ?>
If you are not creating child theme and direct changes into active theme’s file. You will find “Continue Reading” text in template-tags.php file located at wp-content/themes/maxwell/inc directory.
Hope this will helps you.
Thanks !