How to enable allowEncodedSlashes in a ubuntu-based apache server running a website

I'm trying to implement the rule allowEncodedSlashes in an ubuntu apache server running a PHP website. At the moment, the allowEncodedSlashes NoDecode is required to fix some SEO errors.

While I have suceeded in adding the allowEncodedSlashes NoDecode to my localhost, I can't seem to figure out where the config file to put the allowEncodedSlashes in;