The trial balance tab at the top of the screen in Lacerte is where you go to link the files. As previously mentioned, however, it is not the most useful tool. The coding does carryforward from year to year, but depending on the number of accounts and summarizations you need, it may not be worth it. 

Pretty sure I can do it at least as fast as in excel, just data input, no linking, but everyone is trying to automate more these days, so we're using it.