I'm not sure how one would go about using them, unless you send a message and ask to be included in a collection.
To be honest I'm not sure collections have much of an impact on eBay, some are featured on the home page, and you can sometimes find them featured in the sidebar in searches, but I suspect their impact on actual sales is fairly minimal - the giftseditor appears to be soley dedicated to creating collections, but if you look at how long they've been a member, how many collections they've created, and then look at how many followers they have (890), you can see that interest in collections is pretty low (a pretty decent percentage of people who 'follow' things like this don't actively engage with what they're following on a regular basis, so there might be say 200 people who will look at a new collection).
It's hard to determine what their oldest collection is, but the oldest they can be is a bit over 2 years, each with maybe around 30 products, and although I only looked at a few, views ranged from about 2000 to 17000, so ultimately being featured in one couldn't hurt, but probably won't help much, as even blogs and Pinterest boards with followers in the hundreds of thousands don't often result in huge spikes in sales for featured items (they can, but they can also have no effect at all).
