Syntax.
pdnsutil import-tsig-key NAME ALGORITHM KEY
Example.
pdnsutil import-tsig-key foobar HMAC-SHA256 jS0fB3jI9eU1zW0sB1hQ2mK4jI8fR2dCgG4xB7mS4oG0uE5zN5oG5aS2vE7sT2dS
Syntax.
pdnsutil activate-tsig-key ZONE NAME {master|slave}
Example.
pdnsutil activate-tsig-key example.com foobar master
If you use an external backup dns server like netnod.se, that's how you can configure it.
pdnsutil activate-tsig-key example.com foobar slave