Before you can analyze a policy, you must understand the players and the context. The players might include lawmakers advancing policies, federal agencies tasked with implementing policy, the President directing her/his administration, the courts interpreting law, and outside groups (big or small) attempting to influence policymakers. The context will include information on the problem needing a policy remedy, the current policies in force, and proposed changes to policy. These background sources can help you understand both.
Once you have solid background information, you can identify the actual policy documents -- that is, the government documents that have the force of law in shaping policy. These might include laws enacted by Congress, presidential executive orders, Supreme Court decisions, and federal agency regulations.
Another important source for policy analysis is research. Policy research documents might include scholarly journal articles and lengthier reports from think tanks and advocacy groups.