Zend certified PHP/Magento developer

Magento 1.9.4.2 Get orders with REST API

My goal is to be able to establish a connection to our Magento 1.9.4.2 REST API, so that I can retrieve orders data from the REST API.

I need help for all stages of making this connection – I have scoured docs but most of the stuff is for Magento 2, and I am not sure how integration works for the 1.9.4.2 version of Magento. I will be accessing the REST API via making calls from an AWS Lambda function.

Please could someone provide me with steps to access the information in the REST API, starting with how I would create an integration and authenticate my requests? I am happy to use the easiest form of authentication available.

If you need more information please let me know, thank you.