header, cell padding – HELP!

hello. i just purchased a theme the other day from theme forest. i have been having an “OK” time with it so far, but there’s something i cannot seem to adjust properly.

i put my own custom logo on the header, and, as you know, they are created for the tiniest logo. now, my nav menu is floating up in space. i am new to theme-ing and to wordpress in general. i was just wondering if anyone here with a good eye could tell me how to adjust the header area to get my nav menu back down, where i go to do this and how much. i know it’s asking a lot…any help would be fantastic! thanks guys ??

xo nico