The first step after signing up for Merch Jar is connecting your Amazon accounts to begin syncing your campaign data. To do this, click the login with Amazon button to be taken to Amazon's login page. Here you'll login to Amazon using your Amazon advertising credentials.
Once your Amazon account has been linked, you'll need to turn on the ad accounts that you'd like Merch Jar to manage in your account settings under profiles, you'll see all of your Amazon and accounts that have been sent to Merch Jar, and you can turn on the ones you'd like to manage with Merch Jar under the managed field, by just simply clicking the switch, so that appears blue.
This will now appear as an ad account that you can access in Merch Jar and see all the campaign data. If you're missing an ad account, click on the missing account banner here and you'll have instructions on how to create a manager account within the ad console to get it sync up with Merch Jar.
From the profile section, you can also nickname all of your accounts to make it easier to manage. Once you've turned on all the accounts you'd like to manage, that data will start to sync, and you can view it now under your dashboard or all of your campaigns and targets and start optimizing your ads.