At the moment our API is available to Platform customers only.
If you are using the Platform tier go to Plugins and locate the option called, Stackla API. Simply click on Install plugin. Once loaded this will be added your Stack.
We have a number of guides and docs to assist you on our Developer Portal located here http://developer.stackla.com/.
If you'd like information on how to access the API please send an email to email@example.com with your stack name and licence information and our sales team will get back in contact with you.