First of all, IPAs usually only have ARM slices because the App Store does not currently accept Simulator slices in uploads.
Secondly, as of Xcode 8.3 you can drag & drop a .app
bundle into the Simulator window and it will be installed. You can find the app in your build products directory ~/Library/Developer/Xcode/DerivedData/projectname-xyzzyabcdefg/Build/Products/Debug-iphonesimulator
if you want to save it or distribute it to other people.
To install from the command line use xcrun simctl install <device> <path>
.
device
can be the device UUID, its name, or booted
which means the currently booted device.