Demo video on how to setup a heart rate workout using a garmin forerunner 305. For this video I’m using a forerunner 205 since the menus to setup the workout is the same as the 305.
Note that the 305 comes with the HR monitor (strap) and has the extra settings for heart rate. Also the 305 uses zones based on your max HR, and does not include your resting HR to determine the zones, unlike the 405.
You can also use Garmin Training Center to customize your zones.