The best way to get to know the features of ACP is to attempt one of the tutorials. There are two tutorials that explain step-by-step how to define and analyze basic composite structures. The tutorials both start off with existing Workbench projects. These sample projects and more information can be found in the ACP Tutorials. Knowledge of Ansys Workbench is a prerequisite.
For information on how to build a composite model from new, see Analysis of a Composite Shell Model.
There are many ways to implement ACP in Workbench. The workflow for modeling composite solid element models is described in Analysis of a Composite Shell Model. Other examples are shown in Implementation in Workbench.
Composite Modeling Techniques offers an insight into modeling approaches for common composite problems.
Explanations and specific information of the ACP features can be found in Features.
Background information on the underlying theory used in ACP is available in Theory Documentation. This is especially of interest for the failure criteria.