You will need to open and account with 2captcha.com.

Once you have an account you should be able to find the API key inside the account under 2captcha API section on the top menu.

Copy the key and paste it inside indexer on the section where it says "Please click to enter your 2captcha key for the best indexing rates" https://www.screencast.com/t/3cBNW39fAMn

After you login into your Index Autopilot account copy the API Key displayed on the right side.

Login into your Syndwire account and navigate under your Profile name> Indexer API key https://www.screencast.com/t/VVtXlBHu

Once in the indexer window, please make sure you turn the Indexer Status ON https://www.screencast.com/t/e21bzUf4uS

Then paste the API key you previously copied from your indexer.

Hit Submit and you are all set.