If you wish to change validators, you must unstake and restake as follows:
- submit a request to unstake your tokens in the Desktop Wallet;
- at the next epoch boundary, you will stop earning rewards for this stake;
- the network will then start an unstaking delay period of 500 epochs (approximately 1-3 weeks depending on the rate at which the network is producing “rounds”);
- after the delay your tokens will be available to do whatever you want with them, including staking to another validator.
This is one reason why it’s important to make an informed decision about the validators you choose.