<%= f.text_field :company %>
Actually, this code means "Create a markup input of type text, with the good name (ex: user[company]) so Rails can handle the parameter easily". No more no less.
Example Output:
<input type="text" name="user[company]">
Bootstrap will envelope then this object with a style provided by CSS. So
1- Ensure your css is loaded into your "application.css"
Usually, you'll need to add style for the form
<%= form_for @resource, html: { class: "form form-inlined" } do |f| %>
And also around your input text field:
<div class="form-group">
<%= f.label :company %>
<%= f.text_field :company, class: "form-input" %>
</div>
This is just an example, but you can see where to put the bootstrap class on each elements.