After placing an ad on Amazon, it usually takes some time to see the ad placement. The specific time depends on multiple factors, such as the time of ad placement, competition, advertising budget, etc.

Generally speaking, Amazon's advertising system will optimize and adjust within a period of time after the ad is placed to ensure that the ad can be displayed to the most relevant audience. This process may take from a few minutes to a few hours.

In addition, if your ad is set to a specific delivery time or target audience, it may also affect the time when the ad placement appears. For example, if you set the ad to be displayed only during a specific time period, you may not see the ad placement at other times.

If you want to see the ad placement as soon as possible, you can try the following methods:

1. Increase the advertising budget: Increasing the advertising budget may increase the chances of ad display, so that the ad placement can be seen faster.

2. Optimize advertising keywords: Make sure the keywords you choose are relevant to your products and have a high search volume, which can increase the exposure of the ad.

3. Check ad settings: Make sure your ad settings are correct, including delivery time, target audience, etc.

4. Be patient: Sometimes it takes some time to see the ad placement, especially when there is a lot of competition.

It should be noted that Amazon's advertising system is complex and the appearance time of ad placement may fluctuate. If you have any questions about ad delivery or need further help, you can consult Amazon's advertising support team.