$ open -a Simulator

Make sure your simulator is using a 64-bit device
(iPhone 5s or later).  You can check the device by viewing the settings in
the simulator’s Hardware > Device or File > Open Simulator menus.

Depending on your development machine’s screen size,
simulated high-screen-density iOS devices
might overflow your screen. Grab the corner of the
simulator and drag it to change the scale. You can also
use the Window > Physical Size or Window > Pixel Accurate
options if your computer’s resolution is high enough.

Create and run a simple Flutter app

To create your first Flutter app and test your setup,
follow these steps:

Create a new Flutter app by running the following from the
command line:

    
$ flutter create my_app

A my_app directory is created, containing Flutter’s starter app.
Enter this directory: