First thing, download Bitcoin Lightning Wallet (BLW), the best wallet on the market. There are others, but no other non-custodial alternative is so well-supported, light, fast and filled with cutting-edge technology as this.
Get a channel on lnbig.com (yes, they will give you a free channel, watch the video to see how to do it -- and remember to ask for the smallest possible channel size):
Get some free satoshis just to get a feel of how it works -- because everything on the internet is supposed to be free, right? (No.)
You'll need to fill your channel with more than 20000 satoshis to be able to spend anything. That's because of an idiosyncratic requirement of current Lightning Network channels: they demand a 1% "deposit" to be kept on each side of the channel so cheaters can be punished if they ever try to break the protocol. This requirement is going to be dropped when the protocol is upgraded to a new, safer version, but for now you'll have to earn more sats before proceeding to the next, more fun step: spending and playing.
If you have bitcoins on an normal on-chain wallet, you can skip this painful process of earning free satoshis and just push some of your own money to Lightning directly by following this guide.
Now -- with sats or not -- you're done. You can enjoy the world of instant transactions over the internet with real sound money backing everything. Even if you don't have satoshis to spend for now, you have a real Lightning channel of your own now, and it's ready to receive money.
Enjoy the network. For now it's all just play, not much serious ways of earning or spending money, but that's about to change.
As soon as you have enough money on your channel, if you want to confirm it's working you can play poker against others at lightning-poker.com (and you can even increase your bag of sats), show your sports' knowledge by betting on microbet.fun or buy some lightning.gifts for your friends (be sure to show this guide to them first).