Sometimes there are multiple transactions that can be categorized to the same category. Instead of categorizing each transaction individually, you can utilize the batch categorization feature in Puzzle.
1) Find all of the transactions that you want to categorize/recategorize (if recategorizing make sure transactions are not finalized).
2) Click the "Select All" box on the left hand side above the transactions.
3) Click the "Categorized" button at the bottom of the screen to assign a new category and change the existing categorization.