API Key creation can be performed by an Administrator.Administrator at your Site. You can check the Administrator Security Settings found in the Setup Menu if you are an Administrator. The users with the designation of Administrator in the Security Settings marked as True are able to create an API key. If that isn't you, reach out to one of the users with that access.
To create an API key, you'll want to determine what the API key will be used for. A best practice to follow is to create a new user account with a username that is unique to the use case for the API. For example, if you are going to use the API key to open dispatches, you might call it Dispatch_API or if you are going to use it to submit pitch actuals, you could call it Production_API. Once you give the user a unique username and password, mark that user as an Administrator.
You'll see a 'Generate New API Key' button which will automatically create the API key for you.