To place category ads on Amazon, you need to follow the steps below:

1. Log in to your Amazon advertising account: First, you need to have an Amazon advertising account. If you don't have an account yet, you can visit the official website of the Amazon advertising platform and follow the instructions to register.

2. Select the ad type: On the Amazon advertising platform, there are several different ad types to choose from, including Amazon advertising, brand registration, brand content, and category ads. You need to select "category ads" as your ad type.

3. Create an ad campaign: On the advertising platform, you need to create an ad campaign. When creating an ad campaign, you need to select the category you want to place, specify the ad budget and delivery time, set keywords and ad creatives, etc.

4. Set an ad goal: When creating an ad campaign, you need to set an ad goal. Depending on your needs, you can choose different ad goals, such as increasing sales, increasing exposure, or increasing click-through rate.

5. Set bids and budgets: In an advertising campaign, you need to set the bid you are willing to pay for each click and the total budget for the ad. You can set appropriate bids and budgets based on your needs and business situation.

6. Optimize advertising campaigns: Once your advertising campaign starts, you can monitor and optimize your advertising results at any time. You can optimize keywords, adjust bids and advertising creatives based on advertising data.