When someone dies there are things you must do in the first few days:
Get a medical certificate - you’ll get this from a doctor (GP or at a hospital) and it’s needed to register the death.
Register the death - you should do this within 5 days of the death - you’ll then get the documents you need for the funeral.
Arrange the funeral - you can use a funeral director or do it yourself.
Sorting out the person’s affairs, eg selling their property, can be done later - see Wills, probate and inheritance.