Modern programming frequently requires the use of APIs (Application Programming Interfaces). Yet many programmers struggle when trying to learn APIs. We ran an exploratory study in which we observed participants performing an API learning task. We analyze their processes using a proposed model of API learning, grounded in Cognitive Load Theory, Information Foraging Theory, and External Memory research. The results provide support for the model of API Learning and add new insights into the form and usage of external memory while learning APIs. Programmers quickly curated a set of API resources through Information Foraging which served as external memory and then primarily referred to these resources to meet information needs while coding.