Adding class to the webform submit button
I think that you have to do something like this (add an array):

$form['actions']['submit']['#value'] = "click to become a member", array('attributes' =&gt; array('class' =&gt; array('btn'), 'style' =&gt; array('CUSTOM STYLE DIRECTLY') ));


I'm not really sure if is there is the right place the you have to add that code, but that generally it's this code:

, array('attributes' =&gt; array('class' =&gt; array('btn'), 'style' =&gt; array('CUSTOM STYLE DIRECTLY') ))