Help setting up custom script - how do I install python modules?

[DZMM]

Apologies for exposing my true programming level, but I'm struggling to get this script https://gist.github.com/JonnyWong16/2607abf0e3431b6f133861bbe1bb694e workin with custom user scripts.  The bit that is stumping me is how to install the modules (requests, xmltodict and plexapi.server) at the start:

 

# Description:  Sync Plex playlists to shared users.
# Author:       /u/SwiftPanda16
# Requires:     plexapi, requests, xmltodict


import requests
import xmltodict
from plexapi.server import PlexServer

Can someone take pity on me and help please.  I've got some playlists setup that will save me tonnes of time if I can sync them between accounts.

 

Thanks