To create a Carousel Style, follow these steps
1. Navigate to onMessage, select a website from the websites dropdown
2. Click on the styles tab
3. Scroll down to the Carousel Category
4. Click on 'add Carousel'
5. Enter title as well as select the Carousel type
6. Configure the settings for the Carousel
7. Click save

If you would like to know which content types can be used with which Carousel types, please read the following KB article
What types of Content can be used in Carousel Styles?

To apply the Carousel:
1. Navigate to your website in onMessage
2. Click the wrench icon on the page which you wish to apply the Carousel
3. Select edit Style
4. Click on the compatible content block to which you want to apply the desired Carousel Style
5. Use the dropdown selection to select the Carousel Style you want to apply

To apply a carousel to a Master Layout:
1. Navigate to your website in onMessage
2. Select the Master Layouts Tab
3. Click on and edit the Master Layout you wish to add the carousel to
4. On the left-hand side, select the Styles button
5. Click on the block you wish to apply the carousel to
6. Use the dropdown selection to select the carousel you wish to apply