Hopefully you have 5 different tax files saved ... one per person ... and you did not use the same tax file for everyone.
Do you have the 2017 tax file on your computer?
It ends in .tax2017. You need that to transfer into 2018.
First thing you do is start a new return and it should find all your 2017
files and ask if you want to transfer them.
Here's how for Mac:
https://ttlc.intuit.com/questions/1901265-transfer-last-year-s-return-into-turbotax-for-mac
Here's how for Windows:
https://ttlc.intuit.com/questions/1901506-transfer-last-year-s-return-into-turbotax-for-windows
