Daniel,
Simple. Before you put the fields in the form, create a
Select Query using the two tables, pulling the info fields
from the tables into the query grid. Be sure to pull the
Foreign Key field (it will be a Primary Key in one table,
and the field in the other table that relates it) from the
RELATED table into the query first. Then whatever other
fields you need in the order you'll use them. Then, you
create the form using the Query as the source, rather than
trying to use two tables (which doesn't work). You can
have as many forms as necessary from any table, depending
on their usage. Often, you'll have one that is an entry
form, entering the basic data; then, you may have one that
puts in related info, but you want to show the original
info, such as, say, Company Name, address, phone, etc.
Then you create the query as above, using Company Name
from the second table as the first field in the query
(since it's a Select Query, it Selects the related data
from the related table where the Company Name is the
primary key).
Bernie