Transverse Anderson localizing optical fibers (TALOFs) is a unique optical fiber that guides light by a phenomenon known as Anderson localization (AL). The core of a TALOF is very different from that of a typical optical fiber in that the core is made up of a completely random profile in the transverse direction of light propagation while remaining invariant along the fiber. This random arrangement of the core leads to tightly confined modes of propagation that are significantly smaller than the fiber's core diameter. There have been many questions on the interplay between nonlinearity, gain, and AL, and this work attempts to answer some of those questions. This dissertation first studies the nonlinear four-wave mixing (FWM) process in TALOFs. It illustrates the possibility of generating unique photon pairs, which can be used in various applications, including quantum information processing. The second part studies the gain properties of a ytterbium-doped TALOF (Yb:TALOF) to determine if lasing is possible in this fiber, with potential application in broadband or broadly tunable lasers.