We get frequent complaints about bloggers not being able to see the Blogger Layout. If you have migrated from an old Blogger account to the New Blogger (formerly Beta) account, your blogs will still be using the old classic template. To check whether your blog is using the old classic template or the New Blogger template, refer to Old classic Blogger template or New Blogger template?.
If you are still using the old classic Blogger template, and will like to migrate the blog to use the New Blogger template so that you can use the Layout to customize your blog easily, this is the way to do it. In the Dashboard, click TEMPLATE, then under the TEMPLATE tab, click the CUSTOMIZE DESIGN sub-tab, then click UPGRADE YOUR TEMPLATE. Select a suitable template, then click SAVE at the top of the page.
Even if you don’t intend to use the standard Blogger templates, but use a modified New Blogger template like 3 column template for New Blogger (formerly Blogger Beta) or 3 column templates for New Blogger modified by Charlemagne Stavanger, you should still first upgrade to a standard New Blogger template, then use the instructions in Backing up and changing New Blogger template.