Generating the leads using email is already activated on your instance; you need to set up the correct email alias on your sales team. To activate the Contact us page to generate the leads, go to Apps, remove the application filter, search for contact, install the Contact Form application.
You will be redirected to contact us page at
The Tanks message will have appeared as soon as visitor fill the Contact Us form and click on Send button, you will get a lead created in CRM, as follows: