The campaign is planned but not yet started?
You can find the campaign in by navigating to the Campaign Tab. Afterwards click on planned. Click on the title of a campaign to edit it. You will enter the campaign mask where you can make any changes you want. Everything will be safed automatically.
The campaign has already been activated?
Then you´ll find the campaign in Campaigns -> running. Click on the title and enter the campaign editor. Make your desired changes. If you want to change the products or stores of the campaign, you have to click on the little pencil-icon in the upper right corner to do so.
As a store manager you are not able to edit targets or products in active campaigns in the moment.