Current gene-editing tools, including CRISPR and transposon systems, serve various purposes for treating genetic diseases. However, they lack precision in inserting large DNA sequences into specific areas of interest. A novel class of genetic elements, CRISPR-associated transposons (CAST), were recently discovered to be capable of performing DNA insertions via RNA-guided transposition. CASTs merge the precise targeting capability of CRISPR systems with the ability to transport large DNA cargos from transposons, showing significant potential as an innovative gene editing tool.To realize the potential of these novel CAST systems, little is known regarding how elements of CAST systems are assembled and how those elements act together to perform DNA integration. This thesis describes efforts made to structurally characterize each protein component from a type V-K CAST from Scytonema Hofmanni (ShCAST) and to elucidate the underlying molecular mechanism through a combination of biochemical studies and single-particle cryogenic-electron microscopy (cryo-EM). Importantly, the structure of the transpososome, an integration complex containing all CAST components, is presented here. Insights provided by the structure of this complex are used to inform a comprehensive mechanistic model for the activity of the complex, including targeting and regulation. The model reveals how CAST proteins collectively act as a molecular machine to insert DNA at a genomic target site. The results from this study provide novel avenues for the rational optimization of CASTs for highly efficient gene insertions with single base-pair resolution, a critical goal in the field of gene therapy.