I have used Access but have never before set relationships up and am having some trouble understanding the process.
For a simple introduction to modelling data in a relational database you might like to take a look at Relationships.zip in my Dropbox public databases folder at:
https://www.dropbox.com/scl/fo/0scigd3r48hx5xrev2jrf/AB0-GMdTgMAO5O1cGdr3QW0?rlkey=ib6bs6g9jqcrywwzivur3265t&dl=0
This little demo file uses a simple hypothetical medical prescriptions database, and illustrates how relationships are built up across a database to model the underlying reality with related tables, each of which models a real-world entity type. You'll see that some tables model relationships rather than physical entity types. In the database relational model a relationship type is really just special kind of entity type.
Where a table models a relationship type the relationship is usually many-to-many, between two or more tables. For example the DrugForms table models the many-to-many relationship between Drugs and FormTypes, as a drug might be available in one or more forms, tablet, capsule etc., and each form will apply to many drugs,
Many relationships will be one-to-many, however, in which case the relationship type is not modelled by a separate table, but simply by means of a foreign key in the referencing table referencing the primary key of the referenced table. An example of this is the relationship between Patients and PatientPrescriptions. Each patient can have many presriptions, but each prescription can apply to only one patient, so the PatientID foreign key in PatientPrescriptions references the PatientID primary key of Patients. Note that a numeric 'surrogate' primary key must be used her rather than the patient's name as personal names can be duplicated, even if combined with other columns. I was once present at a clinic when two patients turned up within minutes of each other, both female, both having exactly the same names, and both having the same date of birth.