How can I get an answer from one sheet to link to another sheet to be completed?

I have a main registration form and have done medical and dietary forms as well. What I want to do is when you answer 'yes' to "Do you have any medical conidtions or take medication" on the registration page, it will then open a link to the medical form for completion. Once this form has been completed, I then want it to return back to the main registration form. Is this possible???

I am very novice with this so please keep instructions as simple as possible.

It's not possible to have a form opened and go back to the previous one to continue filling the data. 

However, you may use the iFrame widget to display the other form and ask your user to fill it out and then continue filling the main form, please follow these steps: 

1. First get the link to the other form you want to link, this guide will help you doing so: https://www.jotform.com/help/401-Where-to-Find-My-Form-URL 

2. Then add the iFrame Embed widget to the main form and insert the link to the second form you want to get filled. 

Link to the widget: https://widgets.jotform.com/widget/iframe_embed 

This guide will help you adding the widget to your form: https://www.jotform.com/help/252-How-to-Add-a-Widget-to-Your-Form 

3. You may also need to conditionally show this second form, so this guide will help you doing so: https://www.jotform.com/help/316-How-to-Show-or-Hide-Fields-Base-on-User-s-Answer 

This way you will display the second form to your users so they can fill it out and then continue filling the main form. 

To view the submitted data, please check this guide: https://www.jotform.com/help/269-How-to-View-Form-Submissions 

I hope this helps.