<% @posts.each do |p| %>
    <div class="col-sm-6 blog-item">
        <div class="thumbnail">
            <a href="#">
              <img class="img-responsive" src="https://unsplash.it/700/300?random" alt="">
            </a>
            <h3><%= link_to p.title, post_path(p) %></h3>
            <!-- <p class="lead">
              by <a href="#">Heber Sandoval</a>
            </p> -->
            <p><i class="fa fa-clock-o" aria-hidden="true"></i> Posted on <%= p.created_at.strftime("%B %d, %Y") %></p>
            <p><%= truncate p.content, length: 100 %></p>
        </div>
    </div>
<% end %>

<% @posts.each do |p| %>
    <div class="col-sm-4 blog-item">
        <div class="thumbnail">
            <a href="#">
              <img class="img-responsive" src="https://unsplash.it/700/300?random" alt="">
            </a>
            <h4 class="text-center"><%= link_to truncate(p.title, length: 40), post_path(p) %></h4>
            <p><i class="fa fa-clock-o" aria-hidden="true"></i> Posted on <%= p.created_at.strftime("%B %d, %Y") %></p>
            <p><%= truncate p.content, length: 100 %></p>
        </div>
    </div>
<% end %>

Change columns in posts index pages to 3 and added truncated method to the title property.
Change columns in posts index pages to 3 and added truncated method to the title property.
