i want to modify the sidebar. how to do that?

Go to Appearance>Editor>Sidebar.php and remove the following code:

<aside id="archives" class="widget">
<h1 class="widget-title"><?php _e( 'Archives', 'inkzine' ); ?></h1>
<ul>
<?php wp_get_archives( array( 'type' => 'monthly' ) ); ?>
</ul>
</aside>
<aside id="meta" class="widget">
<h1 class="widget-title"><?php _e( 'Meta', 'inkzine' ); ?></h1>
<ul>
<?php wp_register(); ?>
<li><?php wp_loginout(); ?></li>
<?php wp_meta(); ?>
</ul>
</aside>

it is not recomended to edit themes directly;
rather create a child theme for the customization.
https://codex.www.ads-software.com/Child_Themes

however, instead of editing the file, try using widgets in the corresponding widget area; https://codex.www.ads-software.com/WordPress_Widgets

this should remove the default output and only show what widgets you have dragged into the corresponding widget area.