Go to Appearance ➡️ Customize ➡️ Header ➡️ Logo.
Upload a version of logo under “Logo header (Dark)” This should be a logo that works well on white background or on images.
Upload another logo under “Logo Header (Transparent)” This logo is used on home page variations where the transparent header section is above the images. Therefore this logo should work will on image backgrounds.
Logo Height / Width
You can use either square or horizontal logo, although horizontal logo variation is ideal.
The recommended logo height is 32px and any logo that you upload will automatically be adjusted to render at this height.