Plugins not showing up on the page

Hi, I am really new to Grav. I need to make some tweaks to an existing website developed using Grav.

I need to install a few plugins, specifically 'mobiledetect' and 'simplesearch'. However they don't seem to do anything when I install them via dashboard(admin plugin),nothing has shown up on the webpage. Are plugins theme-specific? I am after solutions that don't involve the cmd if possible( so working directly on the dashboard only)

Yes, they need to be implemented in a theme in order to work.

For example, this is how the pagination plugin is implemented in one of the themes. Might help if you need to implement the plugins yourself.

{% if config.plugins.pagination.enabled %}
    {% include 'partials/pagination.html.twig' with {'base_url': page.url, 'pagination': allPosts.params.pagination} %}
{% endif %}

Both plugins have usage information in readme:

Mobile Detect

Simple Search