I don't see it in ACP because I thought it will only appear there if I install Utlimate SEO URL mod which I do not have installed.
According to the DIY instructions
Once all files are edited and uploaded, if you are using the Utlimate SEO URL mod, then just go acp and activate the mod (phpBB SEO extended settings).
Otherwise, hit phpbb_seo/phpbb_seo_related_install.php while logged in as admin and founder and install.
You can then do so set up in phpbb_seo/phpbb_seo_related.php, look for :
var $limit = 5;
var $allforums = false;
var $check_ignore = false;
I just edit the settings in phpbb_seo_related.php directly.
Am I doing this correctly? Should it be available in ACP even though Ultimate SEO URL mod is not installed? I don't see the mod available for inclusion under Module Management in ACP