That’s a pretty broad question because potentially there are a lot of things to be done. If Dad left a will it will contain some instructions on what needs to be done but oftentimes there’s not a lot of specific instructions. If Dad had a trust (and it was properly set up at the beginning) it will provide more details of what needs to be but usually not a lot of day-to-day instructions. If there was an attorney associated with that trust the law office can provide additional guidance be cautious as most attorneys will charge to provide advice and the hourly rate can be several hundred dollars. You should seek out the help of a tax professional since much of the work needed is familiar territory for a qualified professional. If you are seeking a qualified tax professional or (new) estate planning attorney look for someone who will provide an initial appointment at no charge to determine what you need to do next.