[Plugin: Related Posts Thumbnails] Can I use this as Widget?

I did put the php code in a extended text widget. it looks working. but it displays only vertically in a row.

Okay. I managed the display css.

but the widget is only visible in post.php
I placed the widget in a general footer that show identically on every pages in wordpress.
but the widget is invisible except the post page.

any ideas?

I enabled shortcodes in text widgets (just do a Google search) in my functions file then just added the shortcode to a text widget.