1. Download pets theme from drupal.org
2. Add pets theme folder in your website's site/theme folder.
3. Visit your website then go to appearance, Make a pets theme as a default theme by clicking on "set default" link.
4. you can upload your website's logo by visiting yourwebsitename.com/appearance/pets/setting/"Logo image settings"/upload your website's logo.
5. Now your default theme is a pets theme. To upload the header and body image, go to appearance/pets/setting/advanced settings/ upload header and body images.
6. If you want to add social networking sites in your website's header region then go to appearance/ pets/ setting/social icon/check "Show Social Icon"/add url of respective networking sites.
7. If you wish to display 1 or 3 blocks (as given in theme screenshot), create your blocks by visiting yoursitename.com/admin/structure/block and creating a new block using "Add block". You must assign these block to Content first column, Content second column or Content third column based on your preference. The theme will automatically adjust the width of these blocks based on number of blocks you assign.