While you're creating a project, you can choose to add it to an existing Campaign.
- Access your Admin Dashboard.
- Select "Projects" from the left side navigation.
- Press the "New Project" button on the top right of the screen.
- The fourth item in the Details section will say "Join a Campaign". Click "Select campaign or type to search" to add the appropriate campaign from the list that appears. Once selected it will be highlighted green. (Multiple campaigns can be selected if necessary.)
- When you've selected the right campaign publish your project by clicking the "Publish / Update" button on the top right.
Alternatively, you can also add your published project to a campaign from the Campaign Dashboard.
Article: How do I add an existing project to my campaign?