How do I find my API Key?
I have removed my post, as the information that I shared was not related to what it is that you are looking for. I apologize for any inconvenience. I referenced some information, dealing with some legacy information.
Might be a cart before the horse question. Which version of the api are you using? Since documentation for the legacy api isn’t available publicly, I just want to be sure you’re referring to the right one when you use the term “api key”. Mis-understanding of this has cause a great many a lot of time and effort so it doesn’t hurt to check 
Hi @Trenton_King please see Step 2 of Getting Started with OAuth2 - Keap Developer Portal which directs you to https://keys.developer.infusionsoft.com/apps/mykeys. Thanks!