Adding products to a Tradfri hub

I have a few Cree Zigbee light bulbs and light switches I want to add to a Tradfri hub, but I’m not sure where to start. The Tradfri hub seemed to be discovered; it appeared in the states view of HA/Hass.io, and after entering its API key, the panel disappeared.

I’m not sure what the 1-second-on-2-seconds-off repeating pattern is supposed to do with Cree light bulbs, but after 3 or 4 times they flash.

To use Tradfri with HA, do you need a steering device, or can you just use the Tradfri hub and bulbs?