How to change the code of created control

I am new to CakePHP and i am struggling with how/where to create a template for the FormHelper control.
The code generated when i baked my users table, for the add new user form is:
echo $this->Form->control('Username');
which uses:

<div class="form-group input text">
<label for="username">Username</label>
<input type="text" name="Username" maxlength="100" id="username"/></div>

I want all my controls to have the classes and the col div in between, such as:

<div class="form-group">
<label for="username" class="col-sm-2 control-label">Username</label>
<div class="col-sm-10">
<input type="email" class="form-control" id="username" placeholder="Username">

Having read the documentation, it appears that i can provide a custom template name:
templates - The templates you want to use for this input. Any templates will be merged on top of the already loaded templates. This option can either be a filename in /config that contains the templates you want to load, or an array of templates to use.

The issue i have is i dont know what the format of the template file will looklike, and also is this the correct approach.

I hope this has made sense

Thank you in advance