Enabling Expression scripts for use with scripted fields in kibana

Hi, I am having trouble installing the lang-expression plugin to elasticsearch, the error i am getting when i run "plugin install file:///D:/lang-expression-2.2.1.zip" is this: "ERROR: plugin 'lang-expression' cannot be installed like this, it is a system module" I am trying to install this because i was getting the error message: "Discover: script_lang not supported [expression] lexer_no_viable_alt_exception: null" in kibana when trying to use scripted fields to calculate a new field. What is the best way to enable these scripts on a cluster?