It's really easy:

• You go to the Splinterlands website
• You log in with your Hive username (via Keychain or username + password/posting key)
• You can start playing for free with a 'borrowed' set of cards that's immediately available to every player!

Then, if you like the game and want to earn 'real' money/cards/rewards, you can buy the 'Spellbook' from the Shop page. This gives you the first 10 cards that you OWN yourself and aren't borrowed anymore. Whenever you win Credits or DEC you can buy more cards and grow from there :-)

A Spellbook costs 10$, and can be paid in PayPal, but also with Hive or any other crypto after clicking 'Crypto' :-)

I hope you'll take a look and try it out! Let me know if you have more questions :-) Cheers!