First decide what device you want to use:
xcrun simctl list
This will give you a list of devices:
-- iOS 12.0 --
iPhone 6 Plus (AD61D26E-456A-4B4C-9470-B6C362AC140Q) (Shutdown)
Choose the ID (eg. AD61D26E-456A-4B4C-9470-B6C362AC140Q) you want (you can create your own device using xcrun simctl create
if you want).
Boot the simulator with that device (replacing YOUR-DEVICE-ID with the ID)
/Applications/Xcode.app/Contents/Developer/Applications/Simulator.app/Contents/MacOS/Simulator -CurrentDeviceUDID <YOUR-DEVICE-ID>
Now you should be able to use simctl to install and launch commands.
xcrun simctl install <YOUR-DEVICE-ID> <PATH-TO-APPLICATION-BUNDLE>
xcrun simctl launch <YOUR-DEVICE-ID> <BUNDLE-ID-OF-APP-BUNDLE>
xcrun simctl help
for more details.