MultiCharts PowerLanguage is very much like EasyLanguage of Tradestation. Which is why you can review the original EasyLanguage tutorials:
https://www.tradestation.com/promo/easylanguage-books/
Keep in mind that PowerLanguage doesn’t support object-oriented programming of EasyLanguage, and some keywords may differ, but should not be a problem to find analogues in PowerLanguage.
Also you can refer to the keyword descriptions and examples in our Wiki:
https://www.multicharts.com/trading-software/index.php/Category:PowerLanguage