I order the witcher 3 DLC yesterday and it show my receipt but the game doesn't show up in my library so I cant download it what do I do??

The 6 DLCs available should appear in your shelf when you click The Witcher 3, right under the patches.

where is my shelf
the game only shows up in my order history

Ok, you are a bit lazy or just new to the site :p
I'll give you the links:
https://www.gog.com/account (All your games are here)
Temerian armor Set
Beard and Hairstyle Set for Geralt
New quest: Contract: Missing miners
Alternative look for Yennefer
Nilfgaardian armor Set
Crossbow Set - Three new crossbows

Hope this helps.

Click on Account. That will load up you games Library (shelf).
Click on your Witcher 3 game.
-----> If you are using GOG Galaxy you need to click on "More" --> "Get Backup and Extras" now - else,
Scroll down to the bottom of the games downloads.
You will see the down loaders for the DLC's listed under "DLC". See the attached image at the bottom of this post.

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EDITS
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If you are using GOG Galaxy and have only just bought the games you might want to close Galaxy down and then restart Galaxy. It might not have updated to your shelf properly. Galaxy is still having teething issues. New, the account is at most 4 days old now.

thanks im new to this site not lazy