I have been sent a collaboration link - how do i save the form into my own account?

It's not possible to do that with the collaboration feature. You may ask the form's owner to add you as a sub user and share the form with that method instead, this way you will have the form shown on your account too although it will belong to the original user. 

Guide: https://www.jotform.com/help/232-How-to-Share-Forms-with-a-Sub-Account-User 

I hope this helps.