During the on-going second long shutdown of LHC, the forward detectors of the ALICE experiment are implementing an extensive upgrade. In particular, a new Fast Interaction Trigger (FIT) has been designed and built. It consists of three sub-detector systems delivering a broad range of online functionalities, and an essential input for event characterization and physics analysis. For instance, FIT will deliver the precise collision time for the TOF-based particle identification, provide the centrality and the event plane information, and measure the cross section of diffractive processes. This note will discuss usage of FIT in the event plane determination during Run 3. A simulated event plane resolution at $\sqrt{\text{s}_{\text{NN}}} = 2.76~\text{TeV}$ is also presented.