As designed in Phala Token Economics, each miner is required to stake at least 1620 PHA per core before mining starts. On testnet Vendetta, to better perform a stress test on Phala network and allow more miners to participate, Phala network will automatically stake for miners after they register.
However, to score a higher rank in the Miner Race, you can earn more points by using better hardwares, staking more tPHA, or simply running for a longer period, e.t.c.. Rules and tutorials of how to stake more PHA to your miner will be published soon before the race is launched.
This protocol is designed to lowered the entrance cost of staking: a miner may turn to other PHA holders, and invite them to stake for him or her. Thus he or she could start mining with less cost. As a payback, part of the mining profits will be shared with the nominators.
The detailed introduction and tutorial of Mining Nomination will be published shortly.