Go to https://gaming.amazon.com and click on Sign in on the top right. You’ll be prompted to sign in with your Amazon account from there.
You should automatically be redirected back to https://gaming.amazon.com. Next, click on “Link Twitch Account” on the left side.
Click on “Link accounts” when the pop-up appears.
You’ll need to either Log in or Sign Up depending if you have an existing Twitch.tv account.
Once you’re in, you’ll be asked to confirm the link of your accounts.
Navigate to my profile at https://www.twitch.tv/trvlmike and click on Subscribe (and follow).
You’ll be asked if you want to use your monthly free subscription. Click “Yes” to subscribe for one month at no additional charge. Note that this does not renew automatically.