Best way to train openings for beginner?

"... Review each of your games, identifying opening (and other) mistakes with the goal of not repeatedly making the same mistake. ... It is especially critical not to continually fall into opening traps – or even lines that result in difficult positions ... Read many annotated game collections ... By looking at entire games, the aspiring player learns about openings, middlegames, and endgames all at one fell swoop. Playing through annotated games spurs improvement as the reader learns how good players consistently handle common positions and problems. ..." - NM Dan Heisman (2007)
web.archive.org/web/20140627062646/https://www.chesscafe.com/text/heisman81.pdf
"... the average player only needs to know a limited amount about the openings he plays. Providing he understands the main aims of the opening, a few typical plans and a handful of basic variations, that is enough. ..." - FM Steve Giddins (2008)
"... I am not a big fan of weaker players memorizing lots of opening lines they will never play. However, it is quite a different issue to spend a small amount of time learning how to play your openings a little better each time they occur. A long journey begins with a single step. ..." - NM Dan Heisman (2005)
web.archive.org/web/20140627023809/http://www.chesscafe.com/text/heisman50.pdf

This blog will be so much helpful for anyone who reads it. you'll get an understanding on what to do and why should i start like this. check it outhttps://chessgaja.com/2023/06/01/how-to-win-at-chess-with-the-ruy-lopez-and-sicilian-openings-a-guide-for-beginners-from-a-grandmaster/

Familiarization of main lines and sidelines. Modern Chess Openings 2008 by Nick de Firmian. I have been using it until now actually. Many are using it, they just do not say that they use it. Thank me later. Game databases are meant for chess professionals and the endless possibilities will take up a significant amount of time. One very bad thing about the book is that it does not cover the London system. Everything else is fine. Best regards from the Philippines.

In the Queen's Gambit, if I remember it well, Beth Harmon memorized all Sicilians from the Modern Chess Openings book. She was a beginner. "Poor brain", said her best friend Jolene.

Suppose, for example, you play and lose a game that started with 1 e4 e5 2 Nf3 Nc6 3 Bc4 Nf6 4 Ng5 d5 5 exd5 Nxd5. After the game, you can look up the suggestion to play 5...Na5 instead of 5...Nxd5.
"... I am not a big fan of weaker players memorizing lots of opening lines they will never play. However, it is quite a different issue to spend a small amount of time learning how to play your openings a little better each time they occur. A long journey begins with a single step. ..." - NM Dan Heisman (2005)
web.archive.org/web/20140627023809/http://www.chesscafe.com/text/heisman50.pdf
It might be added that MCO itself is becoming less useful for this sort of purpose. For a number of decades, it was considered appropriate to revise it about once every nine years (on average). However, the last revision was about 15 years ago. It has, for example, (as far as I can tell) no discussion of 1 d4 d5 2 Bf4.
"... For new players, I cannot recommend books that use [an encyclopedic] type of presentation [of opening theory], because the explanatory prose that elaborates typical plans and ideas is usually absent, thus leaving the student without any clear idea why certain moves are played or even preferred over other apparently equivalent moves. .... For inexperienced players, I think the model that bases opening discussions on more or less complete games that are fully annotated, though with a main focus on the opening and early middlegame, is the ideal. ..." - FM Carsten Hansen (2010)
“... [First Steps: 1 e4 e5] is a fun and informative book. ...” (2018)
chesscafe.com/book-reviews/first-steps-1-e4-e5-by-john-emms/

I see people talking about 'match results'. Surely this is of little use to beginners, which is what the poster wanted to discuss.

#16. Beginners confuse why opening presented to him to her does not appear in real games. MCO, and encyclopedic openings books will instantly teach what openings are all about a lot of branches of branches of moves. Will instantly teach that one has to have an opening repertoire.

Planning and purpose of each move a general strategy book will do that job. Heavily starts on the middle game. That would make one understand your opening repertoire better. Just like Beth Harmon. */winks.