By default, Isadora will output video to each display at that display's resolution and refresh rate, so if your computer sees the display as a 1080p 60Hz screen, you don't need to do any additional configuration.
You'll be able to see what Isadora sees your external display as in Output > Stage Setup
Here's an article on Stage Setup in Isadora (English).
Here's a video tutorial on Stage Setup in Isadora (English).
You may want to use the Zoomer actor or the FFGLPanSpinZoom actor to reposition your videos because a video with an aspect ratio of 16:9 is not going to 100% fit the shape of a screen with an aspect ratio of 2:1. In case you need to do any Projection Mapping to ensure that your content (with a 16:9 Aspect Ratio) fits nicely on your display (2:1 Aspect Ratio), here's a projection mapping Isadora tutorial video in Spanish.
In terms of general configuration for an Apple computer being used for an Isadora project/production, you can follow the setup steps in my macOS Isadora Show Computer Setup Guide (English) to turn off some pesky settings and such. (For German-speakers, here's an older macOS setup guide (German) by @SchaubühneVideo that may have some more technical steps that I didn't think of.)