Googling it, there is a tutorial from Adobe: How to create bulleted and numbered lists in InDesign | Adobe InDesign CC tutorials
Detailed help is in the Online Help: Create bulleted and numbered lists in InDesign
If you already have read these but could not get it to work, we need more details.
Here's a step by step tutorial I wrote up for a past student: https://www.rockymountaintraining.com/adobe-indesign-numbering-chapters-subheads-tables-fi gures/ . After you read through the blog post come back and read this:
Your situation is much simpler: you only need two levels. So looking at the table below, you would set up two styles: Maybe Head 1 (in place of Chapter title) and Head 2 in place of Subhead 1). And you would leave the word Chapter out of Head 1 since you don't need leading words. Don't forget to name the list, and make sure both levels are using the same name.
This article at InDesignSecrets shows how to set up multi-level lists. http://indesignsecrets.com/multi-level-automatic-numbering-in-indesign.php
This article from InDesign Magazine can also help: http://creativepro.com/working-with-bulleted-and-numbered-lists-indesign/2/