"Quick" fix: Right Click -> view page source ( ctrl+U ), find .css file you changed, open it in new tab and reload ( you should see change in place you've made it )

ONLY in development mode add php fn time() in place of version 
wp_enqueue_style( $handle, $src = '', $deps = array(), time() ,  $media = 'all' )

Delete cache if you use caching plugin.