It's difficult to see just what you need to do without knowing a bit more
about the real-life situation behind the database.  However, it seems maybe
that you manufacture and inspect some sort of product.  I'm don't see the
need for three tables based on my limited understanding of your project.  If
a product has a list of parts or manufacturing operations you would probably
have the product in one table, and the parts list or manufacturing
operations in a separate related table.  A product could have any number of
parts or operations, so the related table for these details is part of good
relational database design.  It does not seem that this is what you are
doing.  From what I can tell the Specs and the Inspection Result are
attributes on the Product, and it could well be that you need just one
table, but as I said there is not enough information about the situation to
allow specific suggestions about the design.
I see that you have two other posts in this forum, one about a continuous
subform that you cannot add to the main form.  Again, details are lacking
about, for instance, how you are trying to add it to the main form and what
happens when you try.  Another thread is about hiding controls on the
subform based on the main form.  In general, the way to reference a subform
control from the main form is Forms!FormName!SubformName.Form!ControlName.
Your questions suggest that some resources for review and study would be
helpful.  This link is to a basic tutorial that provides a concise
explanation of database elements and how they work together:
http://allenbrowne.com/casu-22.html
This link takes you to a page with Tips for Casual Users, among other
things.  I recommend browsing the articles.
http://allenbrowne.com/tips.html
Also, the same site contains a good list of links to articles, tutorials,
and so forth:
http://allenbrowne.com/links.html
The Access Web Page link is a good source of more information, but there are
many other fine sites listed.