first you will have to create a steam account.
After same thing steamworks.
After you will have to fill out a long form, company form, fax, etc... long but mandatory.
Then you need the terms and contracts like confidentiality policy, nothing more normal.
Once you have created your account, that your cancaire and fiscal informationtions, as well as the company information have been verified, that it can take 30 days, you could configure your game.
Then it will start to be complicated, so first you will have to download the steamworks sdk and therefore this sdk will have to put it in the game (basically it is all the scripts and models to generate and download your game on steam.)
to find it you have to go to the official steam page.
you will have to build the game modify it, so that it is accepted on steam there are explanations for how to do it.
then we will have to figure out a little bit the steam work features that come before the store.
these are features... it has a lot for example steam cloud, team keys, you also have to manage the steam ranking, steam cards etc. a lot of things like that, that you can configure on the steamworks.
and then you can configure the page of your store so where you put the game. (you can also put a publication date if necessary)
and you will only have to prepare the release of the product and manage the marketing etc....
and there will be stuff left behind but I gave the answer
good luck