Hello, I am creating a new template but I have not figured out how do I put it on the menu in order to select from frontend

Hi there,
please describe your problem detailed as possible. We need more informations:
1.) Live Url
2.) Screenshot

I created a new model of template changing parameters from the model default but do not know how to connect it to the menu so that a member can choose

demo site: www.zumbaparty.it/socialnetwork/

What do you mean with "model".
Did you created a new Template style, or what?

But you can assign different theme styles to different menu item, watch the video:
www.joomlaplates.com/support/documentati...profile-to-menu-item