Hello!
1. First of all, increase the height of the header area to fit your logo there: find the CSS file that holds styles for "#header .line1" element and change "height: 80px" to "height: 98px" in these styles.
2. Now re-size the logo placeholder to match the width and the height of your logo. Find the CSS file that adds styles for "#header .line1 .logo a img" element and change the width from 179px to 250px, and the height from 70px to 98px:
Code:
#header .line1 .logo a img {
background: transparent url(../../skin/ideal_responsive/css/../images/main_sprites_lg.png) no-repeat left top;
width: 250px;
height: 98px;
}
3. Finally, remove the white spacing above the logo to fit it into the header section. Edit the CSS file that defines styles for "#header .line1 .logo" element and change "padding-top: 16px;" to "padding-top: 0px;".
You can tweak these styles further to add necessary spacing around the logo (if needed).
Does this help?