#
#-----[ REMOVE ]-----
#
PHPBB3_ROOT/portal/block/calendar.php
PHPBB3_ROOT/styles/prosilver/template/portal/block/calendar_2.html
PHPBB3_ROOT/styles/subsilver2/template/portal/block/calendar_2.html

#
#-----[ UPLOAD ]-----
#
CPOY root/styles/prosilver/template/portal/block/calendar.html TO PHPBB3_ROOT/styles/prosilver/template/portal/block/calendar.html
CPOY root/styles/subsilver2/template/portal/block/calendar.html TO PHPBB3_ROOT/styles/subsilver2/template/portal/block/calendar.html

#
#-----[ OPEN ]-----
#
portal.php

#
#-----[ FIND ]-----
#
include($phpbb_root_path . 'portal/block/calendar.'.$phpEx);

#
#-----[ REPLACE WITH ]-----
# P.S. You can remove the line.
#
//include($phpbb_root_path . 'portal/block/calendar.'.$phpEx);

#
#-----[ FIND ]-----
#
$user->setup('mods/lang_portal');

#
#-----[ AFTER, ADD ]-----
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$user->setup('calendar');
// Display phpBB Calendar next events.
// If you want to see more events than 5, only change the number.
display_next_events(5);

#
#-----[ OPEN ]-----
#
includes/functions_calendar.php

NOTE:
This file does not need amend.
Please use source file in phpBB Calendar v0.1.0.

#
#-----[ OPEN ]-----
#
language/en/common.php

#
#-----[ FIND ]-----
#
    // Event Calendar
    $lang = array_merge($lang, array(
       'EVENTS'      => 'Events',
       'WEEK'      => 'Week',
       // minical short day names   
       'mini_datetime'   => array(
            'Su'      => 'Su',
            'Mo'      => 'Mo',
            'Tu'      => 'Tu',
            'We'      => 'We',
            'Th'      => 'Th',
            'Fr'      => 'Fr',
            'Sa'      => 'Sa',
       ),
    ));

#
#-----[ REPLACE WITH ]-----
# P.S. You can remove these codes.
#
/*
    // Event Calendar
    $lang = array_merge($lang, array(
       'EVENTS'      => 'Events',
       'WEEK'      => 'Week',
       // minical short day names   
       'mini_datetime'   => array(
            'Su'      => 'Su',
            'Mo'      => 'Mo',
            'Tu'      => 'Tu',
            'We'      => 'We',
            'Th'      => 'Th',
            'Fr'      => 'Fr',
            'Sa'      => 'Sa',
       ),
    ));
*/

#
#-----[ OPEN ]-----
#
styles/prosilver/template/portal/portal_body.html

#
#-----[ FIND ]-----
#
<!-- IF S_CALENDAR_WEEK -->
		<!-- INCLUDE portal/block/calendar.html -->
<!-- ELSEIF S_CALENDAR_NEXT_EVENTS -->
		<!-- INCLUDE portal/block/calendar_2.html -->
<!-- ENDIF -->

#
#-----[ REPLACE WITH ]-----
#
		<!-- INCLUDE portal/block/calendar.html -->

#
#-----[ SAVE & CLOSE ]-----
#

P.S.
Purge the cache.