I'm still using 4.0, but the princple is the same.If its a small file, that's good. Rather than going through the whole file, matching and merging; and assuming you are adding a file that has some duplicates in your large file; make a note of the ID# for the "head of household" and his wife. Import the small file, use the alpha search to find your target individual.You should find the old and new person together.make a note of the ID# for the new individual. go to "merge" and use the "find" function to merge the two individuals.That will now give him 2 spouses; write those ID#s down, and merge them. (You can edit the notes and sources immediately after you merge so you don't have to go back and do it later). Leave the merge screen and go to the main person again. Use the edit and "order children". You will see any duplicated children; mark down the ID numbers again, and merge them the same way. any child that has a spouse will show the duplicated spouse and their ID#'s. Merge them.
And so on down the line.I have a VERY large file and find it much easier to do it person by person. If I do an automated search, it always misses someone, and my finger gets tired of "next". There are always hundreds of them no matter how narrow I make the options.
Good luck. PS. Always use the check/repair on a new file before you merge. you never know.