I've actually got a video focussed on @splinterlands specifically coming out soon... but until then: they have a great FAQ over on https://splinterlands.com/?p=faq ... but for now the best advice I can give you is to just join the game and play a few games.
Seriously... You've already got a Hive account and can sign in with that using KeyChain or HiveSigner. Signing up is probably the hardest part ;-)
Then: Work through the tutorial (they've got a step-by-step in-game tutorial) that literally teaches you the basics (my girlfriend picked it up in less than a week)... and then when you're ready, pay the $10 for the spellbook.
The only down-side: Without any SPS staked (and in-game token that you can buy on HIVE-Engine though), you'll need to wait about 35 days before you can buy any packs... but until then you can grab some cards on the secondary market at @peakmonsters (https://peakmonsters.com/).
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