Anything labeled "Secondary Source" will provide background, interpretation, or commentary.
The assignment has three parts, all of which require outside sources:
Strategy tip: it may be simplest to start with #2: a policy or program you know about, then work backward to #1: the problem it addresses.
What is U.S.C. or U.S.C.A.? Example: 42 U.S.C. 1751
What is Pub. L. or P.L.? Example: P.L. 111-296
What is C.F.R.? Example: 7 C.F.R. § 245.6
Try putting the legal citation into WestlawNext to find the original document. Googling will often work too, since these are government documents.