How to input data to two tables that has a many-to-many association

Hello, I'm quite new to retool, so please I need all the help I can get. I have two tables store and category, on my Postgres db with a many-to-many association. Postgres automatically created a join table for their relationship. How do I associate records from store and category?
I have tried so many options such as trying to input records(store and category ids) directly in the extra join table, but nothing is working.

What does your insert statement look like? Can you share more information?

my current implementation is inserting records into category and store separately (pls find attached the screenshots). I try to use a multi-select listbox to grab the storeId and categoryId of the records needed to be associated, and then store them into the _CategoryToStore table, but I'm getting some weird error. I feel there might be a more straightforward way to implement a many-to-many association

Hey @Ifeoluwa_Clement, can you share the error that you are getting? And to be clear this error is when you are attempting to insert the data into the join table (ie: just the store and category ids)?