First you have to purchase the Spellbook. Once you have a Spellbook you can start earning rewards for winning matches and completing daily quests. Rewards can be DEC, Cards or credits. You can also receive SPT for blogging here. As you accumulate cards, SPT, DEC and Booster Packs you will start getting SPS airdropped every day. You can also purchase SPS and stake it and you will get SPS as staking rewards.