The Blogger Theme comes with the option to use styled text for your site title and tagline or to upload a logo image of your choice.
To configure these options, from your WordPress dashboard click on Appearance > Customize. Open the “Site Identity” menu.
Styled Text Logo
Enter the name of your blog into the SITE TITLE field and then enter your blog’s tagline into the TAGLINE field. Click “save”
You can also use an image for your logo. If you choose this option, then your logo will be displayed in place of the SITE TITLE and the TAGLINE content.
Click the ‘Select Logo‘ button and choose your logo file from the Media Library.
The ideal logo size for the theme is 300px × 100px. We have disabled the forced cropping option to allow for more flexible logo sizes. However, we recommend that you keep the image logo to no wider than 250px so it looks like good with theme.
Also there is option to change Sticky Header Logo (MOBILE HEADER AND STICKY LOGO) and Favicon here.