The cytoskeleton, a dynamic network of biopolymers with their associated cross-linking and motor proteins, is responsible for stabilizing cell shape and driving cell movement. This paper aims to provide an overview of the theoretical and computational approaches that have been developed to understand the dynamic behaviors and underlying mechanisms of actin-based cytoskeletal networks, connecting their microscopic structure to macroscopic performance across various scales, with implications for the observed nonlinear stress-strain relation, viscoelastic properties, stiffening induced by active motors as well as their biological functions in important processes such as cell adhesion, motility, and mechanosensing. In the future, more sophisticated constitutive theories, continuum level, and molecular dynamics-based simulations of biopolymer networks are expected to provide critical insights for understanding the material-structure-function relation in the cytoskeleton of cells and guiding the development of active biomimetic materials.