The way you want to do a Tail Slide is by taking your front foot, putting it to the right of the board, and grabbing it with your right hand. It's easier if you turn the board sideways once you get sliding, but some people also like to just lean back and slide their tail on the ground. However, this looks far more cool and it's way more fun to do.
The way you're going to want to do a Tail Slide is not too dissimilar from a No Comply, except this time instead of popping your board off the ground, you're going to kind of let the nose pop into your hand. You want to grab it with your thumb so you have it under control. Once you do that, you're going to want to turn your board sideways, slide for as far as your push will allow. So you're going to push off the ground with your right foot, kick out with your back foot, try to get some distance while you have some speed, and after you're done doing that you're going to want to turn your board back pointing in the direction you want to go in. Once you do that, you just want to land your front foot right back on the board. Just make sure not to get too over-extended. Letting your back foot catch up to you is very important on this trick.
If you're having trouble doing a Tail Slide, you might want to try just putting your tail on the ground, grabbing the nose of the board with your right hand, and sliding it for a little bit. See how that feels just pushing it back and forth on the ground so you get a little bit more control and you understand how to do this trick before you go downhill and do it like that.
Also, when you take your front foot off the board, try to keep it by the edge so that it's a little bit faster release. Make sure your front hand is ready so you have a catch. And that's really how you do a Tail Slide.