Having issues with BASE Indexing tables - Please help

I have several tables I imported from Access - The concepts here seem very similar, however what ever I try to get one table to reference another in Relationships, I get errors - Fields are the same name, format, size, etc. Even with similar Indexs. Cant get them to refer to one another. In a One-Many or in a One-One format.

Embedded or connected tables? If connected, to what? (What I’m getting at is which database are they in now?)

Also pls update your question to also provide one specific example of the fields in two tables, (names, types, etc), and how you’re trying to join them. And can you pls add a screen shot of your relationships window?