I think you need to narrow down your questions. Fully answering your post would require posting a major section of a how to manual on FileMaker.
A simple outline for how to create a relationship:
- Define two tables in Manage | Database | Tables
- Click the Fields tab and define the key fields in each table that you want for your relationship.
- Click the relationship tabl and drag from the key field in one table to the key field in another. You can link more than one pair of fields and you can double click the relationship line to bring up a dialog for more options for the relationship.
- Each "box" in the relationships tab are called table occurrences. You can create more than one "occurrence" of a given table in order to create more relationships.
With regards to question 2. You cannot use a script in FileMaker to modify an existing relationship. The only way you can modify a relationship is by hand in Manage | Database | Relationships.
How you "use" a relationship in a script is too complex to answer here as there are many, many ways different script steps "use" relationships.
You may find this tutorial on table occurrences useful: Tutorial: What are Table Occurrences?
Thanks for the reply :)