Welcome to Retool (and programming in general)!
Your case is a pretty straightforward one for many use cases in our apps. If you intend to allow for multiple rows to be updated the GUI action you want to use is Bulk Update via Primary key (but this also works for a single row):
This lets you choose your table's PK directly (which I believe you currently have hidden from your table display). The Array of records to update will be your table's changesetArray, which can be accessed using {{yourTableName.changesetArray}}
Lastly, sometimes you may need to send all of the row data to the query to be able to access unique values/columns, in which case you can toggle that option on in the table's Interaction setup:
