Creating a Many to Many relationship and bringing records into the

If I have a database where my tables are events and audits and I want to be able to have many events and many audits that can be related both ways, I know that there is an intermediary table required, which i have set up. How do I bring the existing data into the intermediary table without creating a new record. The goal is to list certain events that are related to the audit on the audit form. Any help is appreciated very much.