Editing WP htaccess Control - wordpress

Question

I'm currently using the WP htaccess Control plugin for my WordPress website and I would like to make a modification to its code. Presently, each page is accessible via multiple url structures. For example, site.com/page/ is accessible as is site.com/page
I would like to setup the htaccess whereas the non trailing slash redirects to the trailing slash, for every page of the site.
I believe I have the code, but I've seen a couple different variations. I want to make sure I implement the right one, plus I'm not exactly sure how it should be done with this particular plugin.
Do I just add the additional lines to the "custom" section? To my understanding it has to be placed with the rewrite rules, but the custom code I can input only goes to the top.
Currently, the following line is in "custom htaccess":
php_value memory_limit 96M
the entire file is:
# BEGIN WordPress
# WPhtc: Begin Custom htaccess
php_value memory_limit 96M
# WPhtc: End Custom htaccess
# WPhtC: Disable ServerSignature on generated error pages
ServerSignature Off
# WPhtC: Protect WP-config.php
<files wp-config.php>
order allow,deny
deny from all
</files>
# WPhtC: Protect .htaccess file
<files ~ "^.*\.([Hh][Tt][Aa])">
order allow,deny
deny from all
</files>
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>
# END WordPress
thank you