I'm going to explain the theory (got to make supper in a minute) and hope it works for you.
It's brilliant for stuff like sending letters to a whole bunch of people, creating lists, etc. It works by matching a standard form in Word (like a letter, or label template) to the individual data for people (or things, whatever) in a spreadsheet.
Create an Excel spreadsheet with the data - eg name, address, appointment date. You must have a header row - make the column titles meaningful to you.
Create a Word document that is your letter (or list, or label) which contains all the information that everyone needs to have (instructions on how to get to appointment, for example).
Now hit the button/menu option that says something like mail merge or mail merge helper (depends on your version). Choose your "data source" - the spreadsheet you just created and saved.
You will now have the option to add fields from data (the header row column titles) to the standard letter. Put them in the right places - eg. name and address at the top, appointment time in the text etc).
Now merge the documents - you usually want the option to 'edit individual documents' so that you can check all is well.
Your spreadsheet will magically turn into a whole series of lovely personalised letters.
I have written that v. quickly - hope it makes sense. THe tutorials in Word are good and will cover it. Will come back later to see how you're getting on . Good luck!