There is more than one way to access the screens for customizing WordPress Theme Twenty Twelve. In the Dashboard you will see a list of labels down the left side of the screen. You can also go to Appearance, Themes, and click the Customize Tab.
You can check in other themes as well to see if they too have the Customize Tab.
Steps to Customize WordPress Under the Customize Tab
1. Customize Tab: In the Dashboard you can click on labels in the left side of the screen to customize the site. Or you can go to Appearance, then go to Themes.
2. Customize Your Theme: Click on Customize under Themes. The theme you are using will be showing with an image of the theme at the top of the screen. Click Customize.
3. Site Title and Tagline: Set the Site Title and Tagline by clicking on the label that has opened.
4. Header and Background Color: Choose Colors and Header Image from the Customize Tab Menu. Upload a Header Image and choose a Background Color. If you wish to create a custom header image with a logo and upload it please see the article and video on that subject on this site.
Creating the Header: You can create a header in any graphics program. Picasa is one of the easy, free softwares you can use. If you decide to create a header in Picasa please see the tutorials on this site that go into greater detail.
Briefly, you click to select photos or graphics, click to “hold” them in the “tray” in the lower left of the screen, click Create in the menu at the top, click Collage from the drop down menu, choose a length and width or enter one manually (Twenty Twelve will accept header sizes different from the default size so you can make a wide or a narrow header), drag and resize the images, click to Create the collage, then use the Text tools to add header text to it.
You can also go to Appearance and Header to remove the title from the top of the page if you already have the title in the custom header. Although this removes the title and tag line from showing at the top of the site this does not remove it from Settings so the search engines can still read the title.
5. Navigation and Menus: Under the Navigation label click to choose whether you wish to use the default menu or a Custom Menu that have previously created. If you wish to create a Custom Menu please see the article and video that covers that subject on this site.
6. Static Front Page or Blog Front Page: Choose whether to use a Static Front Page or a Blog Posts style. Static front page means the front page will not change when you write new articles for Posts. Choosing the Blog Posts style means the most recent articles Posted will show at the top of the front page of the site.
7. When you are finished click Save.