Adding a Logo to the Home Page

We are finishing up the details of our new website, and I am having trouble uploading our firm’s logo to the upper-righthand part of the homepage. The thing is, I do not want a white background surrounding the logo – I just want the logo itself (and the color of the page surrounding it). How can I go about getting rid of the white surrounding the logo? Also, the positioning of the logo seems to be very limited. How can I situate it in the upper-righthand corner, where I want it?