Action Details
Requirements and how-to articles for Product Hunt's action:

Collections are a way to bookmark and curate products you are interested in. You can also work on collections with others by adding them as a collection curator.

You need this to get it done:

Create Collection
To create a collection, select 'Save' when viewing a product. You can then either create a new collection with that product or add the product to an existing collection.
Add Curators
If you wish, you can add curators who can add, remove and highlight posts in the collection.
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How-To Articles
A list of useful links for you:

Product Hunt Help Center - How do Collections work?
Guide to creating and using collections.
Product Hunt - What is a collection curator?
Explains what curators are, and how to add them.
Link missing here or found errors? Improve How-Tos