There’s not a lot of wiggle room there… Where are you confused? deciding whether to place it in the beginning middle or end?
Google says that it’s not important to have your keyword in the domain anymore, and I believe to a large degree that’s true. However, I still notice domains with a keyword in their name ranking for a lot of longer tail keywords by default that I suspect they wouldn’t rank for otherwise, or at least not as well.
I think that having your main keyword anywhere in the domain is fine. However, I only advise it when the keyword is super generic and very high up the totem pole of keywords. For example, a shoe retailer might have a domain called prettyshoes.com. I think that’s great.
However, I think a domain like bestwomensleathershoes.com is junk, and the exact type of keyword domain scheming that Google targeted in their EMD update a few years back.
I feel like the difference is obvious, but more quantified guidance would be that if there’s a keyword related to your keyword, that you’re considering for your domain, That has a higher monthly volume, that’s probably the one you need to consider for the domain instead.