The header logo can be as tall as header, which is max 90px. You control the height from the original image size. Then just upload in header.
If you need more than 90px, you’ll have to overwrite theme header CSS and align again several elements. In style.css these are commented under menu.
To overwrite default CSS we recommend child theme. To install child theme – you have the instructions in the theme pack.
If you need more help please open an account and add tickets here http://support.wpestate.org/