How install add-on

How install add-on from https://www.home-assistant.io/integrations/ ?
I have hass.io version 0.100.1

They are not addon’s ( these are ) they are integrations.

Select the one you want from the page you linked to and it will take you to an instruction document for configuring it.

Be aware that’s your Home Assistant version, not your Hass.io version. Hass.io is how you installed Home Assistant, and it has a separate version number.

For example, I want to add the weather darksky.
Add to my configuration.yaml file

weather:
  - platform: darksky
    api_key: MY_API_KEY

But nothing happens, maybe something else needs to be done?

Did you replace MY_API_KEY with an actual API key you created as per the instructions?

Of course replaced

Understood, I did not restart HASS
Now everything works