Ruby on Rails

Hello everyone, I just started off with RoR and had a question.

I wanted to link my 'Show All Posts' to my allposts.html.erb which will
display all the posts that are created but I am having difficulty in
doing so. Do I need to define this in routes.rb file. I just want to
display all posts when that link is clicked.

          <ul class="nav navbar-nav">
            <li><%= link_to "New Post", new_post_path %></li>
            <li><%= link_to "Show All Posts", '#' %></li>
            <li><a href="#contact">Contact</a></li>
          </ul>

allposts.html.erb contents
<% @posts.each do |post| %>
<h2><%= post.title %></h2>
<p><%= post.body%></p> <br>
<%= link_to "Show Posts", post  %>
<% end %>