I understand this is a stupid question. I understand the answer should be obvious! I'm new to the writing scene, however, and I would like to know the proper process of going about it.
You must completely finish your manuscript, and be ready for it to be published as-is. There may be some changes requested, they may fix things, but don't submit something you think needs work. Submit a completely finished story.
To understand why, understand the industry. Authors are NOT in short supply! Agents and publishers have to turn down 95% of what they read, the vast majority of stuff they get is flawed. If you are an agent, how do you get through twenty manuscripts from first-timers to find the one you MIGHT be willing to read more of? The only efficient way to do that is to reject things quickly and permanently the minute you detect bad writing. You also reject anything that is described as a "work in progress", because if you want to represent it, you want it done RIGHT NOW, not in three months or a year or never.
These people won't coddle you or mentor you, and a newbie writer is not in the power position. They don't want to babysit you, or nurture you. Their ideal scenario is to find a completed work they can read from start to finish without cringing, with a satisfying ending, that they can start representing tomorrow.
They make their decisions harshly and efficiently, first on your query letter, then on your first chapter or 30 pages or whatever, then on the full manuscript. Finish the whole thing, to the point you can read it cover to cover without cringing yourself, or feeling like something sucks.
Then write your query. Query about six agents at a time. This way if you get any constructive rejections, you can address their criticisms before the next round of queries. Don't blast a hundred agents with your first or ANY query! You can't query them again (unless they offer that.) Most agents will filter out repeated queries.
This way if there is something wrong with your story or writing or query letter, you can try to address that and you have more agents to try. You can iterate several times this way. There are plenty of online sites for finding agents, my approach is to find about thirty that might be interested in my book, and then try them six at a time. Follow their rules for submission; if they ask for ten pages, give them ten, not eleven. If they ask for the first chapter, give them that. If they ask for 30 pages, don't give them 31 pages to "finish the scene".
Prepare yourself emotionally for 100% rejection, but also be ready to send the full manuscript on request.
You do what the submission guidelines say you should do.
ALWAYS find out what is wanted. Some publishers want a 50 page extract, some want it all. They often want their own standards for layout too, so be prepared to alter it as needed.
But, as said above. Never, ever, never, submit work that is not the very best you can produce. And I'd never submit anything which I did not have completed finished, even if I'm only sending an extract.