How do I add non-members to the mailing list & convert them to leads while sending showroom link?

When seller selects lead(s) and click on 'Send Showroom Link' button, a pop-up opens up with the functionality to set price visibility, enter a message etc. There is also an area "Add other Leads" which allows adding non-members to the list of prospects so that they can be sent the showroom link. Seller can enter first name, last name, company name & email id and click on add icon and the non-member will get added to the mailing list.

When seller clicks on 'Send Showroom Link' button, the non-members who were added on the pop-up, gets added to the leads list. They will receive invitation to the seller's showroom.