In order to see your claimed Twitch drops in-game in Warhammer Age of Sigmar: Realms of Ruin, you will need to first be linked to a Frontier account. A guide for this can be found here.
If you have watched a qualifying stream, but have not yet linked your Twitch account to your Frontier account, you will still earn your drops.
Any drops you earn should appear in your Twitch Inventory:
https://www.twitch.tv/drops/inventory
To link your Frontier account to Twitch, you will then need to go here:
https://twitch.frontierstore.net/
Click the 'LOGIN TO FRONTIER' button:
You will then be redirected to sign in. Keep the selection for using your Frontier account credentials, regardless of the platform on which you are playing; cosmetics will apply via your linked Frontier account regardless of whether you play using Steam, Epic, PSN or Xbox.
Enter the registered email and password for your Frontier account and click to log in, to get the prompt below. Click LINK YOUR TWITCH ACCOUNT.
You'll be redirected, and prompted to sign into your Twitch account, after which you will be returned to our Twitch page, and your account should now be linked.
You can unlink and re-link from this page at any time.
In-game, your items should show up for you in your profile (click into your name in the top right of the screen), under 'Customise'.
If you run into any issues with this or require further assistance, please use the button below to contact support.