combining 2 tables

[menewbie]

Let me preface my question by stating that I am a baby when it comes access. Actively looking for training but I have a problem I am trying to push through in the meantime. I will not be offended if you dumb-down the response.
I have 2 tables. Table A has 9 fields. Table B has the same fields as Table A plus 3 additional fields. I am trying to do the following:

a) add all of the rows from Table A to Table B
b) Remove duplicates rows based on the 9 common fields

[ranman256]

Make a 3rd table that has ALL the ffields.
key the 9 fields (to prevent dupes)
add tbl 1
add tbl 2

[menewbie]

Can you explain how to "key the 9 fields"?