Creating a If statement to post a themify image next to a post title

I created a simple blog and I’m using paperclip to be able to add images
to a Post. I installed the ‘themify-icons-rails’ gem and what I want to
do is automatically add a picture icon next to the title of a post when
the post has a image that’s been uploaded, to show that the post has a
image. I’m guessing I would need a If statement somewhere but I’m fairly
new to rails and I’m not sure where to put it.

<%= link_to post.title, post %>

this adds the "Ti-gallery" icon to every post.

Any Help will be greatly appreciated, Thank you before hand. Oh and one
more questions, Is rails Video friendly? i can’t seem to find any
tutorials on uploading videos to a rails app.