Your API Keys are located under Settings, which you can access by clicking on the chevron (down arrow) in the top right corner of your Dashboard once you have logged in.
Administrators and Developers can see API keys. If you cannot, it means you have User, or User R/W access. Contact the administrator of your account for the API keys or to change your access using the User Management page.
How-to video: Where to find your Simplify Commerce API Keys