Settings Logo and Icons for your site :

1. Login to your WordPress Dashboard
2. Go to Appearance > Customizer from your WordPress Dashboard
3. Go to General Settings > Site Name and Description
4. Upload logo image and icon image for your site.

Follow the recommended size to get best result. Logo should be horizontal like 250×80 and Icon should be 512×512 resolution.

Adjust Logo Width :

1. Go to Customize > Header > Logo width (px) and set logo width.
2. Adjust the width to get best result for your site.