The image/logo that come standard with the theme is 218px × 53px in size. If you’re not customizing the theme, you should be able to just replace this image with your logo.
Here’s how to do that:
1. Log into your WordPress account
2. Click on the Appearance tab on the left sidebar in wordpress
3. Then click on the Theme settings submenu under Appearance
4. Then the first setting under the General Settings in Blog Logo
5. Click the Browse button to find your logo
6. Select the file from your computer or media library (depending upon where your logo is located)
7. The once you found the logo and load it don’t forget to hit the Save Changes button
That should fix it for you and get your logo up and running. Best of luck!