This Note is a user's guide to the latest version of the OPUS (Optimal Preferential Utility and Strategies) program. When a set of targets is attacked by reentry vehicles (RVs) and defended by interceptors, this program evaluates the effectiveness of a defense employing preallocated preferential strategies. A stochastic model of terminal defense is used to represent up to two layers of interceptors. The targets can be divided into multiple categories, with different parameter values for each category. The RVs can arrive either sequentially or simultaneously, and they can be accompanied by up to two types of decoys. The defense can employ uniform, tapered, or salvo firing doctrines; and they can use deception with respect to the locations of both interceptors and targets. The optimal offensive and defensive strategies are determined by solving a two-person zero-sum constrained game.