How can I get Twitter Application API Key, API Secret, Account Access Token & Account Access Token Secret?
Please sign in with your account and create an app on Twitter through this link: https://dev.twitter.com/apps and get your own Keys to add.
How to use shortcode inside page templates?
WordPress has a great function,
do_shortcode(), that will allow you to use shortcodes inside your theme files. For example, to output Tweets in a Theme file, you would do this:
<?php echo do_shortcode('[gs_tweet username="wordpress" theme="gstf_theme1"]'); >