Impossible to see it

Hello,
this plugin looks very nice and I think it is exactelly what I’m looking for:
A very nice menu on my blog, but I don’t understand, I don’t arrive to make it working !
Somes explanations :

1 / To install the plugin : no problem.
2 / To activate it : no problem too.
3 / in WP Responsive Menu, I choose a menu, everything else is on YES.
but There is absolut no changement on the blog !?!

I did that on 3 differents blogs on 2 differents hosters, and see no difference.
Where is my error ?
What I did wrong ?
I really appreciate some help, because I’m little blocked.
Thank you for it, sorry for my bad english.

https://wordpress.org/plugins/wp-responsive-menu/