"Forms and Surveys" can be found under your "Community" or "Content" module
Step 1: First, select "Forms and Surveys" from the left menu then click on the name of the form that you want to enable. "Save and Continue" on.
Step 2: Click on "Settings" at the top of the page
Step 3: Within the form settings page, you can scroll down and check the option labeled "Save and Continue"
After enabling "Save and Continue", you may change the link text by entering it in the field below.
Don’t forget to save your settings when complete!
Now at the bottom of that form the person filling it out will be given the option to "Save and Continue Later"
After selecting that button the person will be taken to a page that looks like this with a link they can go to to finish filling out their form. They may also fill in their email in the space provided to have the link sent to their email.
The provided link will expire in 30 days.