How to select the collection which will be displayed on the home page?

To view the collection displaying on your home page, Go to Admin>> Design>> Design>> Home. There you will find home-collections, these are the collections which will be displayed on your site home page.

Firstly, if you want to change the collection displaying in your home, you'll have to create a new collection. Follow the steps mentioned in the below link to know how to add collection-

https://help.storehippo.com/topic/collections