Two-step form completion

How do I have user #1 complete part of the form and then when they save or submit, it sends to user #2 to complete?

You could just set up an email notification that will be sent to the second person that will complete the form, you should also include the edit link of the submission in the email so when he/she opens the link the previously submitted data will be displayed. 

If you will ask the first submitter for the second persons's email address then you will need to set up an email auto-responder that will send to this email address. This guide will help you to set it up: https://www.jotform.com/help/26-Setting-Up-an-Autoresponder-Email 

If the second person will be fixed, for example, some checking the submissions and completing them, then you could set an email notification and include the edit link on the submission. 

This guide will help you to set up an email notification on your form: https://www.jotform.com/help/25-Setting-Up-Email-Notifications 

To include the edit link on the email you only need to open the emails wizard and edit your notification: 

The next step is to click on the form fields option and get the edit link from there: 

The same steps are for the email auto-responder. 

Hope this helps.