I Don’t Want Your Password
As a quick example, I’ll use Stripe to demonstrate the kind of functionality that you’ll usually find included to give access to a third party.
Settings are always a good place to start and then you’re looking for the delegated access section, sometimes called Team/s, Facebook calls it Page Roles, PayPal uses Account access and others use similar options.
The Least Access Possible
Most if not all will give you options for the level of access you can allow to your account, the simple answer is to give as little access as possible or allow greater access for a limited period.