I lost my iPhone, how can I turn icloud on from my computer?

Lost my iPhone and I don't have icloud on! How can I turn icloud on from my computer?!

Do you mean you are not signed in to your iCloud account on your iPhone?
If that's the case - you can't turn it on from PC. Kinda defeats the object of logging in/out of the accounts on your phone

You need to have set up Find My iPhone/iPad on your device prior to it getting lost or stolen. If you did, go to https://www.icloud.com/...cloud.com/ in your web browser. When you log in, Find My iPhone/iPad will immediately begin trying to locate your device.
If not, I suggest you notify your service provider and give them both your mobile phone number and IMEI number.
To prevent your new idevice from being stolen or lost in the future, I suggest you set up Find My iPhone/iPad in iCloud on the device and apply some free anti-theft app like iLostFinder. It will take pics of the thief or finders when she/he tries to open your device and then send the pics to your email.
http://ikeymonitor.com/free-apps

This is exactly what happened to me. You would think Apple would have a way!