Database Mirroring automatic failover

Hi,

I am considering implementing Database Mirroring on SQL 2019 standard edition.

I need automatic failover, so will need a witness instance I assume? The application currently connects using a config file
with the Servername\InstanceName specified.

Can anyone tell me how I can get the application to point to the Mirror instance in the event the Principal fails?

Does the witness instance need a licence?

Thanks,

Zoe