Welcome to the Apple Community.
You can only locate your device when it is logged into iCloud and 'Find My Mac' is enabled, additionally the device will need to be switched on and connected to a wifi network.
Unfortunately, you cannot activate iCloud or 'Find My Phone' remotely.
If the device is wiped by you or another, you may not be able to locate the device (although some have reported they can)
You should also change the passwords on any Apple ID's you have in use on the device. If the Mac is suspected to have been stolen, report it to the Police (if you have insurance ask for a crime reference number).