Please Help!!

I am SOOO confused about how to type in the correct "formula" for a VLookup.
Anyone that can help - I thank you dearly in advance!!! Here's my
situation:

I have two worksheets, and need to import the price for about 3500 items
from one of the worksheets into the other. It is my understanding that a
VLOOKUP will do the job for me, but I just can't get this to work, and have
managed to confuse myself to no end!!!!

Here's what I have so far:

DOCUMENT #1
Column A = Item Number (is already filled in column A)

Column B = Cost (is blank in this worksheet and the values need to be
taken from Document #2 and dropped into this column, based on the item
numbers, of course)


DOCUMENT #2
Column A = Item Number (is already filled in column A for this worksheet)

Column B = Cost (is already filled in column B for this worksheet. I need
to get these values to the corresponding item number in Document #1)


Thank you very much for any help that anyone can give. I have managed to
confuse myself so much that I know this posting is probably confusing for the
person trying to help me!

Thank you for your attention to my problem!