If you find your message and publication content are using a consistent design, you should consider creating re-usable templates. Re-usable templates will save you time by having a design in place, which will give you the time to focus on adding the content.
To create a re-usable template, go to the Content tab, click the 'Re-usuable templates' in the left-hand menu, under the relevant content area. Click the add new template button.
To create a message template, use this guide: Creating an email message - the basics
To create a publication template, go to: Creating a landing page
When done, click 
To use a re-usable template when creating new content, select the template from the 'Template' field.