The first step is to create a new Warranty Template. 

This Template will capture the terms and Title of the Warranty for you to apply to an Inventory Item.

1. Go to Admin  > Inventory >  Warranty Templates.

2. Click New Warranty template:

3. Fill out the terms of the Warranty:

4. Go to Inventory > New Item to create an Inventory Item for this Warranty, to add to Invoices when needed:

5. Add to future Invoices:

6. After the Customer pays, this Warranty will then be tied to the Customer Record:

7. You can see a running list of ALL open warranties in Admin > Reports > Warranty List:

That is it! If you want to follow up with Customer to extend warranties that are due to expire, refer to this article.