Snex9x ex+ is one and only emulator for android. This is available in the Google Play store like other apps.
Here are steps that you need to follow
Click here to Visit Download page. It will open the play store as you can see. Click on the install button.
After that open and it will ask for permission. Click on Allow.
You have done it.
How to Play Games
View this video to known how to download and play game son snes9x ex+