This paper presents the step by step procedure to evaluate Available Transfer Capability (ATC) of the interconnected transmission network using Power World Simulator. Fast and accurate determination of ATC is very important in real time. Various software packages have been developed to evaluate ATC of the given system. Also, there exist linear methods for ATC calculation, which are either based upon DC or AC Power Transfer Distribution Factors (PTDF). These are fast, but do not consider control changes such as generator reactive limits and voltage limits as the transfer limit increases. Another method to calculate ATC is Continuation Power Flow (CPF) method, which can produce accurate ATC values but requires repeated solution of power flow, and hence consumes more time. Also, there is a probabilistic approach to determine ATC, which is carried out by Monte Carlo Simulation. In this paper, PTDF method is explained to find ATC, which is implemented as Add Ons in Power World Simulator to compute ATC. The results are discussed for IEEE-14 bus system.