app/views/mtdevise/account/users/_form.html.erb
<div style="margin-bottom: 25px" class="input-group">
<span class="input-group-addon"><i class="fa fa-envelope"></i></span>
<%= user.text_field :email, required: true, :class => "form-control", :placeholder => "Email" %>
</div>
<div style="margin-bottom: 25px" class="input-group">
<span class="input-group-addon"><i class="fa fa-asterisk"></i></span>
<%= user.password_field :password, required: true, :class => "form-control", :placeholder => "Password" %>
</div>
<div style="margin-bottom: 25px" class="input-group">
<span class="input-group-addon"><i class="fa fa-asterisk"></i></span>
<%= user.password_field :password_confirmation, required: true, :class => "form-control", :placeholder => "Confirm Password" %>
</div>