By simply saying Ok Google, run my task in Tasker (where my task is any of your tasks' name) you'll be able to run any of your existing Tasks with your voice!
You can also say something like run my task with something and other to set %par1 to something and %par2 to other when calling your tasks if you want.
Instead of run you can also use any of these words:
If you want more control over your voice commands you can setup profiles with the Assistant Action event and here you can filter you command any way you like using Tasker Pattern Matching.
You can use this to receive variable inputs for example. You could have a command like run turn off my bedroom lights in 5 minutes with Tasker and then parse that out and have Tasker wait 5 minutes and after that turn off your bedroom lights.
Assistant App Actions is a feature Google allows apps to have in English only for now. I'll add support for other languages as soon as App Actions allow it.
Unfortunately on some occasions Google gets it wrong and doesn't send the command to Tasker. Mostly in cases where a very similar and very commonly used command exists for the Google Assistant itself.
For example a command like run timer in Tasker might be interpreted by the assitant itself and create a timer there instead of running your task called timer.
In those cases you need to change the task name to something more unique or use the "Assistant Action" event with a custom command to trigger it.