Q: An one-time introductory slideshow for all users how do i do it:
The first time each user visits the Apps screen, a slide show will appear instead of a splash screen which will tell the user about various features.
4 slides will come on the very first run of the app. slides will be changed using the swipe gestures
the slideshow will appear only for one time after the very first download.
Check this image as a reference: http://main.makeuseoflimited.netdna-cdn.com/wp-content/uploads/2012/03/HiLauncher6.png?323f2c

A: All you have to do is store a Boolean variable inside the app using SharedPreferences which will determine whether the slideshow has appeared once or not, if so the don't show it again.
For example:
SharedPreferences sp = getSharedPreferences(MY_PREFS_NAME,
        Context.MODE_PRIVATE);
boolean isFirstTime = sp.getBoolean(IS_FIRST_TIME, true);

if (isFirstTime) {

        showSlideshow()


    } else {

        // Go to your main activity
        Intent main = new Intent(Start.this, MainActivity.class);
        startActivity(main);
        finish();

    }

Don't forget to set isFirstTime to false once the slideshow has been shown, and store it in the sharedPreferences
Hope that helps
