Add a menu to an empty activity

You need to inflate your menu. These tutorials show how to use menus. So something like this, and choose a better name than menu_menu:

public boolean onCreateOptionsMenu(Menu menu) {
 MenuInflater inflater = getMenuInflater();
 inflater.inflate(R.menu.menu_menu, menu);
 return true;
}

when you make a menu's layout you need to define it for the Activity you want to place it in. You may do so by:

@Override
    public boolean onCreateOptionsMenu(Menu menu) {
        MenuInflater findMenuItems = getMenuInflater();
        findMenuItems.inflate(R.menu.main_menu, menu);
        return super.onCreateOptionsMenu(menu);
    }

the main_menu is your menu's layout name, and findMenuItems is an optional name.

And to make your menu's items clickable for an About menu and exiting the app you'll need this:

@Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case R.id.aboutMenuItem:
                Intent aboutIntent = new Intent(MainActivity.this, AboutActivity.class);
                startActivity(aboutIntent);
                break;
            case R.id.exitMenuItem:
                finish();
                break;
        }
        return super.onOptionsItemSelected(item);
    }