There are a variety of resources on this site, dedicated to getting you up and running as quickly as possible.
If you have valuable video assets that you are interested in protecting, distributing and monetizing, see Getting Started for Content Provider for additional information on how OSMF can help you achieve your goals.
If you are ready to get started creating an OSMF based player, but need an example to get you going, check out Getting Started for Developers for suggestions on some good places start.
If you are an experienced developer and just want to know the best way to work with the OSMF source code, see Source to learn more about working with the Subversion repository hosted by Adobe.
If you are already comfortable working with open source projects, but want developer documentation, a look at the feature specifications, where to join the developer forums, or how to submit bugs and feature requests, see the Developers Resources section.