check this thread : CJW save plugin and this for step by step : step-by-step
and i know its quite confusing (i feel ya)…, basically you need to download the plugins (smPlugin.js and smPluginMenuAddon.js) → put it in the web folder of your choicescript game (outside mygame folder)
→ and then open the index.html in the mygame folder with notepad (i used notepad++)
→ and then add these lines of code (look at the picture)
<script src="../smPlugin.js"></script>
<script src="../smPluginMenuAddon.js"></script>
→ after that, you can add *sm_init code in your startup file (be sure to put it at the bottom of your variable and achievement code to avoid an error.)
hope it helps 
im quite a noob at coding, and i figure it out after doing it for a while longer after several failed attempt XD. lol
EDIT : how to put *sm_init code :
example : *sm_init Fool's Fantasy | 3