All Ocsigen packages are available via opam, the OCaml package manager.
For client-server applications with mobile support, start with Ocsigen Start:
$ opam install ocsigen-start
Then read the getting started guide.
For traditional websites with minimal client-side code, Eliom alone is enough:
$ opam install ocsipersist-sqlite-config eliom
See the server-side programming documentation.
Browse all tutorials to find the best starting point for your project.