You can associate any pre-existing asset (landing pages, CTAs, blog posts, social messages, etc.) to a campaign from within the Campaigns app.
- Navigate to Content > Campaigns
- Click on the name of your campaign
- Within your desired selection, choose Associate
- Check or uncheck the box next to the content you'd like to associate with your campaign
- Click Save
Each asset can only be associated with one campaign, so adding an asset to your campaign will remove that asset's association with any other campaign.