Once you have created a new campaign, built your audience in the criteria tab, decided whether to include display ads or not, and selected your email editor and template, you are ready to edit your template.
Navigate to Campaigns > Create > Template.
Regardless of which editor you are working in, you can always select Change Template to return to the Template tab and choose a different template. Changing the template, however, will delete all content and edits you have made in the campaign thus far.
Change Template Type
If your template is in the Email Editor (drag and drop editor) but you decide to add personalization tags and/or dynamic content, select Personalize to make your template editable in the HTML Editor.
Once you choose a template that utilizes dynamic content and/or personalization tags in your campaign you must always edit the campaign in either the Studio editor or Code Editor (Legacy); you cannot change to the Drag & Drop Editor (Legacy).