Hi All,
Still a bit new to all this… I’ve been checking over the community and there are lots of posts about using a Virtual Device to trigger an Alexa Routine.
Well I managed to create a Virtual switch the turns on and off when required, however, this will not show up in the list of motion or door sensors.
I know that it has to be a sensor not a switch for alexa to see it.
Any ideas?
Start with the community created FAQ. Follow all of the steps in the FAQ exactly in the order given. 
This is a very popular integration and a lot of people are using it. But you can’t use just a virtual switch. You have to use a virtual device which is both a switch and a sensor, so that turning on the switch makes the sensor look like it is open and turning off the switch makes the sensor look like it is closed. The FAQ will walk you through the steps.
I use a lot of “Simulated Alexa Switches” - a custom developed Device Handler by Brian Pierron
It is described here: [Release] Virtual Alexa Switch/Button
NOTE:
After examining the FAQ link mentioned by JDRoberts and drilling down to the “theSmartcave” article theSmartCave, it turns out it also recommends the Brian Pierron device handler.
(I started using the “Simulated Alexa Switch” back in December 2018)