When switching account to get a switch bonus, you'll need to close and switch an old account using CASS. This is done through the new bank you're switching to. All payments, Direct Debits and standing orders are switched over to the new account.
You'll usually need to fulfil certain criteria to qualify, such as depositing a certain amount (either as a one-off or monthly), using the bank's app, or opening one of its linked savers. It's important to check this criteria carefully before switching, as failure to complete any of the steps will mean you don't get the switch bonus.
Note: Some account types won't qualify for switch bonuses – for example, current accounts linked to a mortgage (such as NatWest's One Account).