You have to use a smart app to do it. There are two provided in the official smartthings mobile app marketplace section that work very well. (Note that routines used to be called “hello home phrases” or “hello home actions.” They’re all the same thing.)
- open the mobile app
- choose the marketplace section.
Three) choose the smart apps tab)
Four) choose “lights and switches”
Five) scroll down until you see the apps to have a switch activate a hello home phrase. install it, and then you will be able to associate the virtual switch with the routine.
There is a much fancier version of the same smartapp by the same author called “Alexa helper” (because it was first used by people who had the Amazon echo). It lets you set up six switches at once instead of just one, with all kinds of filters and rules for them. However, it has not been officially published to the marketplace yet, so here is its link in the community-created wiki: