With the settings available in Gecko Customizer, you will be able to upload and customize your site logo. You can find these settings in WP Admin -> Gecko -> Gecko Customizer -> Site -> Logo Section.
Logo Image section:
Here you will find settings to upload logos separately for desktop and mobile devices.
If you want to change the color of tagline text and logo text you can change it in WP Admin -> Gecko -> Gecko Customizer ->Theme -> Header -> Header colors section settings.