In order to set up the integration with OptimizePress, they require you to provide your own API Key and Token. You can find a little bit of explanation on their website here: https://www.optimizepress.com/8-new-features-in-optimizepress-update-2-5-2/
To get your own API key, we require a developer account which can be created here: https://constantcontact.mashery.com/member/register
Once you've created a developer account, you will need to register an API key here: https://constantcontact.mashery.com/apps/register
You can use the following values to set up your API Key:
Once you have an API key, you can get an Access Token by going to our API Tester and clicking on Get Access Token. You can find the API tester here: https://constantcontact.mashery.com/io-docs
If you have any questions, please let me know!