You can start by looking at a blog post like this one.
We would also recommend reading chapters 1-3 of Design for how people learn by Julie Dirksen.
Universal Design for Learning Guidelines
Blog post introducing four instructional design models
Choosing the right methods and platforms (SIL)
Design For How People Learn by Julie Dirksen is a great book for beginning instructional designers.
In order to adapt materials well, you need to have a good idea of the context for which the original materials were created and a good understanding of the context in which you want to use these materials. Craig Ott's book Teaching and Learning Across Cultures walks you through a number of dimensions (cognitive, worldview, environmental, individual preferences) that are good to consider when thinking through how to adapt training materials.