Crave utilizes a consensus algorithm called Proof of Stake (PoS) to create and validate block transactions. Staking is the 'mining' of PoS coins, so to speak. Rather than using expensive and dedicated mining hardware as in the case of Proof-of-Work coins, such as Bitcoin, staking is performed through your Crave wallet software and is based off how many coins you hold. The more Crave that you own and stake, the more 'mining' power you have.
Staking starts by storing your coins in your wallet, which needs to be online. Once your coins reach maturity, you can begin staking by opening your wallet and unlocking it for staking. Your wallet will then start competing with other wallets for signing the next block. If you are chosen to sign a block, you will get a staking reward, which is 4 Crave. After this, the coin age of those chosen will be zeroed out, and will have to mature again.
There is no minimum amount needed to stake Crave, but again - having more coins staking will give you a larger weight, and therefore a higher chance to receive the staking block reward.