Season 4, Episode 5 is titled "Adaptation" . It centers on the "trio" (Charles, Oliver, and Mabel) being manipulated by their doubles and features a major cliffhanger.
If you are looking for instructions on how to "put together" a three-way conversation on your phone, here is the standard process: How To Do 3 Way Call on iPhone [S4E5] Three-Way
While many shows have an episode 5 in their fourth season, a few are specifically associated with "Three-Way" dynamics or titles: Season 4, Episode 5 is titled "Adaptation"
The request "[S4E5] Three-Way" could refer to a few different things, most likely a specific television episode or a technical guide for setting up a three-way call. [S4E5] Three-Way