Logo (Header):
You can upload your own logo image at your Dashboard –> Appearance –> Customize -> Theme Options -> Logo upload
If You use Free theme
You can upload your own logo image at your Dashboard –> Appearance –> Customize –> Site Identity
The logo of the themes, i created them with Adobe Photoshop, the logo file (.psd format) is included in theme (find in Logo folder in the downloaded package). If you love the default logo, Adobe Photoshop is required to edit.