Can i upload my logo even though i have a wp theme?

In your theme CSS change this (copy and paste):

#header #header-info {
position: absolute;
top: 40px;
left: 308px;
width: 390px;
text-align: center;
visibility: hidden;
}

That will hide the text in your header, but will still be searchable by Google. For placing a image you just copy and paste this code:

<div id="header-logo">/"><img src="<?php bloginfo('template_directory'); ?>/images/logo.jpg" border="0" alt="My Logo" /></div>

into your index.php file after it says:

div id="header">

Save.

Then add this into your CSS:

#header-logo {

position: relative;
float: right;
right: 150px;
}

Save. Then that’s it. You can of course tweak where the logo is going to be placed in the last code. Just change the numbers in the header-logo CSS.