When you first start building your new Divi theme website you’ll find that any logo you upload will be very small.
You can easily change that in the Theme Customiser.
Log into your WordPress Dashboard, then:
Divi > Theme Customiser > Header & Navigation > Primary Menu Bar.
You will use both the ‘Menu Height’ and ‘Logo Max Height’ controls to increase your menu height. It can be a bit confusing because you’d think that if you wanted a bigger logo, you’d just adjust the logo max height. But this is not the case.
Menu Height determines the height of your primary menu bar.
Logo Max Height determines the percentage of space within that bar occupied by your logo, so you need to change the menu height first before you’ll see a result in the logo height.
Remember that you’ll need to upload an appropriately sized (and optimised) logo. Before adjusting, the logo is set at 43 pixels high, reducing to 30 pixels once you scroll, so if you want it 2-3 times as high, upload a logo that’s 80 -130 pixels high.
Have a play around and let me know if you have any questions.