Retrieving Time Machine backed up files
You can use the Migration Assistent found in Application/Utilities folder. This program will allow you to copy files, pictures, folders, programs, settings and more from a Time Machine backup. 

Edit:
Open Migration Assistent and choose Time machine option, then click continue. Connect the time machine backup disk and choose it from the menu. Then select things to copy. 

Read more here:
https://support.apple.com/en-us/HT204350

This is a similar question:
Restore files from Time Machine to a different Mac